Old Age According to Inō Tadataka. From Dull Merchant Ledgers onto the Far Roads of the Edo Era – Straight into the History of Cartography.
Inō Tadataka wanted to know the size of the Earth – along the way he gave his country its first modern map.
The eleventh of June, 1800, still before dawn. A small party sets out north from Edo: a few students, servants, packhorses bearing wooden chests full of instruments. At its head walks a man of an age at which people of that era had long since drawn up their wills and been forgotten. He is fifty-five. He walks with even, deliberate steps, as if measuring them out – and he is measuring them. One step, two, three. He will go on counting for the next seventeen years.
In the Edo of those years, fifty meant something other than it does today. Most of his contemporaries had long handed their businesses to their children and withdrawn into the background. He was only just beginning.
His name is Inō Tadataka. For more than three decades he brewed sake and traded rice in a riverside town, lent money at interest and kept his books with such precision that he turned his wife’s declining family house into one of the wealthiest in the district. He had earned the privilege of wearing a sword, normally reserved for warriors, and could have died in comfort as a respected old man whom no one beyond his town would ever have heard of.
Instead he handed his fortune to his son, packed his books and went to the capital to study astronomy under someone nineteen years his junior. Not tea, not poetry, not pilgrimages to temples – the usual pursuits of a wealthy retiree of the day. Mathematical astronomy, the hardest and most hermetic science of the age.
And now he is heading north. And here begins the strangest thing in this whole story.
Tadataka does not set out to draw a map of Japan. The map will be a by-product, something that comes out along the way. That same map will later astonish Europe, serve the shōgunate as a military secret, and vanish for two centuries before turning up in an archive on the other side of the world. Meanwhile the man with whom it all begins sets off because of a single question that has kept him from sleep for five years. As simple as a child’s question and at the same time the greatest one can ask about the ground beneath one’s feet: how large is the Earth? Not in the philosophical sense. In the precise, measurable sense, expressed as a number.
Today most of us know that number. In his day no one in Japan knew it, and those who tried to guess offered wildly varying and contradictory figures. Tadataka meant to obtain it in the only sure way available to him: to walk across a piece of the planet and count his steps. This will be a story about that measurement. But even more – about how life can begin anew at the very point when most have already written it off.
The Boy from Kujūkuri
Inō Tadataka (伊能忠敬) comes into the world in 1745 in the village of Ozeki on Kujūkuri Bay, in Kazusa Province – today the eastern coast of Chiba Prefecture. His mother’s family, the Koseki, have governed the village for generations and live from the sea; his father is an adopted son-in-law from the neighbouring Jinbō family. The boy is given the name Sanjirō.
There is no idyll. When Sanjirō turns six, his mother dies, and his father – an in-married outsider – must return to his own family. He leaves his son in the house of his dead wife and only takes him in four years later. Popular biographies from the Meiji era dressed this period in anecdotes about a prodigy poring alone over accounts at night; modern scholars, led by Watanabe Ichirō, treat such tales with caution, since little source material survives from Tadataka’s childhood. One thing seems certain: the boy counted well and counted willingly.
In 1762, at the age of seventeen, Sanjirō marries Michi, heiress of the Inō merchant house of Sawara in the neighbouring province of Shimōsa, four years his senior. He enters her family as a mukoyōshi (婿養子), an adopted son-in-law, and takes the name by which history will remember him: Inō Tadataka.
Thirty-Two Years of Account Books
The Sawara of the late eighteenth century is a busy river port on the Tone-gawa, a transhipment hub on the water route to Edo. Rice, sake, salt and fuel flow from here by barge straight to the markets of the capital, and along the Ono-gawa canal stand warehouses with whitewashed walls. The Inō house ranks among the town’s foremost: a sake brewery, the buying and selling of rice, fuel, loans. Except that its glory is already behind it. The young son-in-law inherits a business in need of repair.
He repairs it over three decades – without fireworks, by the method of everyday merchant’s diligence. From 1781 he also serves as nanushi (名主), headman of his part of Sawara, answerable to the shōgunate’s officials for taxes, disputes and order. When the great Tenmei famine comes in the 1780s and whole villages die out in the northern provinces, Tadataka opens his granaries and pours out rice from his own stores. Tradition passed down in Sawara holds that the town did not lose a single inhabitant then. For his services in repairing the Tone-gawa embankments and his help during the famine, his liege lord, the hatamoto Tsuda, grants him the privilege of bearing a surname and a sword – an honour normally reserved for the warrior class.
The scale of his success is best conveyed by a figure handed down through family tradition: when he gives the house to his son in 1794, the Inō fortune is said to amount to thirty thousand ryō. The sum cannot be verified in any ledger today, but modern Japanese estimates convert it to three to six billion yen – well over a hundred million złoty, though such a conversion, given a gap of nearly three centuries, may of course be somewhat misleading. Even if the legend rounded upward, one thing is certain: at fifty, Tadataka had built a fortune large enough that he could have spent the rest of his life merely spending, and never working again.
Four Years’ Wait for a New Life of His Own
He makes the decision much earlier, back in 1790, as a forty-five-year-old: he will hand the business to his son and devote himself to learning. His family and community need four years to let him go – a man on whose accounts and management half the town depends does not leave overnight. In the meantime he writes a short family testament for his son Kagetaka: three principles, among them honesty and forbearance toward people. Nothing about profit.
In 1794 he formally enters inkyo (隠居), the retirement of the head of the house, and takes a new name, Kageyu. Inkyo itself was nothing unusual – in Edo-period Japan the elder passed responsibility to his successor and withdrew into the background, an institution as old as the merchant houses themselves. What was unusual was something else: what Tadataka intended to do with his freedom. Another wealthy retiree would have taken up a collection, a garden or patronage. He chose mathematical astronomy – a field so hermetic that only a handful of people in the whole country even knew what it was. A year later he packs his books and instruments, leaves Sawara behind and rents a house in Edo, in the riverside district of Fukagawa.
A Pupil Nineteen Years Older Than His Master
In the capital he knocks on the door of Takahashi Yoshitoki (高橋至時), the newly appointed astronomer of the shōgunate. Yoshitoki directs the work of the tenmongata (天文方), the office responsible for the calendar, celestial observation and the study of Dutch scientific books. He is thirty-one, comes from Osaka, from a poor samurai family of the lowest rank, and was raised to the top by sheer talent: he is just then carrying out the great calendar reform of the Kansei era. And before him stands a fifty-year-old merchant from the provinces, asking to be taken on as a pupil.
Yoshitoki quickly realises that the newcomer has not come merely to kill time. Tadataka builds beside his house in Fukagawa a private observatory that an official bureau would not be ashamed of, and night after night he measures the altitudes of the Sun and the stars, spending his days over the calculations of their movements. It absorbs him so completely that he is reluctant to leave the house – his master jokingly calls him Suiho-sensei (推歩先生), “the master of reckoning the stars,” for suiho means precisely the computation of the courses of celestial bodies. In that joke there is admiration. The latitude of his own house the retired merchant determined so precisely that military surveyors a hundred years later would correct his figure by a mere twenty-three seconds of arc.
The Question of One Degree
During his studies Tadataka comes upon a problem that electrified his master and scholars in Europe alike – the very one with which this story began: exactly how long is one degree of the meridian? Japanese textbooks give contradictory values – thirty ri, thirty-two ri, others still. And without that number there is no accurate calendar, no reliable prediction of eclipses, and no answer to the simplest possible question: how large is the sphere beneath our feet.
Tadataka solves the problem like a merchant. If it is not known, it must be measured. From his observations he determines the difference in latitude between his house in Fukagawa and the calendar observatory in Asakusa, then measures the distance between them and brings his master a finished calculation. Yoshitoki shakes his head: the stretch is far too short, measurement error swallows the result. A reliable figure will require a distance of hundreds of kilometres along the meridian. Best of all – from here all the way to Ezo (today’s Hokkaidō), in the far north.
And here a private obsession meets reason of state. It is the turn of the century; Russian ships appear ever more often off the northern coasts, Adam Laxman’s embassy has already knocked on the closed country’s door, and the authorities in Edo discover with unease that they have no proper maps of their own northern frontiers. Yoshitoki turns his pupil’s dream into a state project: he obtains official permission to survey the route to Ezo and the southern coast of the island. With one condition – the costs will be borne largely by the interested party himself. Tadataka accepts the terms without haggling. All his life he had earned money. Now at last he knows what for.
Forty Kilometres a Day
The first expedition – the one from that June morning of 1800 – lasts a hundred and eighty days and covers, there and back, about three thousand two hundred kilometres. Along the Ōshū road the small party moves at a pace that would command respect even today: forty kilometres a day, day after day, taking measurements. At this stage they measure distances chiefly by paces, hence Tadataka’s deliberate, even gait. Popular tradition holds that he trained a stride exactly sixty-nine centimetres long; period sources do not directly confirm that particular figure, but the principle itself – the pace as a standard of measure, calibrated over years – is well attested.
The method rests on two pillars. The first is dōsenhō (導線法), traverse measurement: from point to point one measures distance and bearing relative to north, with the route marked by bamboo poles bearing paper streamers. The errors of such a chain, however, accumulate with every link, so a second pillar is needed – kōkaihō (交会法), the method of intersection. From several stations one sights the same distant object: a lone tree, a temple roof, a mountain peak, and best of all Fuji, visible from a large part of the country. If the lines of bearing do not converge at a single point, an error has crept in somewhere and must be caught. At night astronomy takes over: a quadrant with a telescope measures the altitudes of stars crossing the meridian, and from them Tadataka computes the latitude of the station to fractions of a minute of arc. In time heavier equipment is added: kenawa (間縄) measuring lines, iron chains resistant to stretching and damp, and finally the distance wheel ryōteisha (量程車) – ingenious, though useful only on hard, level roads – of which there are few in mountainous Japan.
The terrain resists. On Ezo the Erimo cape proves impassable, and on the map there remains an honest annotation: fusokuryō (不測量) – “not measured.” That small note says more about Tadataka than many a word of praise: where chain and quadrant did not reach, neither did the pen. He preferred to leave a blank space rather than a fabricated line.
The answer to the great question comes after the second expedition, in 1801. One degree of the meridian is twenty-eight point two ri – about 110.7 kilometres. Yoshitoki compares this result with the figures from the Dutch translation of the works of the French astronomer Lalande, the latest European knowledge to have reached Japan. The values agree almost perfectly. Master and pupil rejoice like children. They had reason to: we now know that the retired merchant’s measurement differed from the true value by about two parts in a thousand.
The Map Its Author Could Not Look Upon
In the autumn of 1804, in the great hall of Edo Castle, they spread on the floor a map of eastern Japan – the sum of the first four expeditions, sixty-nine large-scale sheets, plus overview sheets. The shōgun Tokugawa Ienari himself views it. The author is not in the hall. A merchant, however wealthy and however deserving, has no entry where the military aristocracy sits. Tadataka waits outside the system that is just then admiring his work.
Four days later word arrives: he receives a modest post within the structures of the bakufu and a fuchi (扶持) stipend, a salary paid in rice – at the rate of rations for ten people. Little for a man who could afford to finance the expeditions out of his own purse – but it is no longer about money. From this moment the survey of Japan is an official state undertaking; historians estimate that over the whole seventeen-year project roughly four-fifths of the cost was ultimately borne by the shōgun’s government. A private obsession had become reason of state in writing.
That same year takes from him his master and teacher. Takahashi Yoshitoki dies at the age of thirty-nine – his contemporaries said he had worked himself to death over the translation of Lalande’s treatise. The pupil, nineteen years older, will outlive him by fourteen more years. Oversight of the project will pass to the dead man’s son, the very young Takahashi Kageyasu. Let us remember that name, for it will return in this story in circumstances no one would wish for.
Ten Expeditions
Then come further years and further routes: the coasts of western Japan, Shikoku, Kyūshū with its islands, the inland roads. Ten expeditions between 1800 and 1816, by various reckonings from three thousand seven hundred to nearly four thousand days in the field. The total length of the surveyed routes reaches forty thousand kilometres – as much as the circumference of the Earth, whose size Tadataka had asked about at the start – of which he himself walked about thirty-five thousand, since auxiliary teams measured some stretches in parallel. All of it meticulously recorded: twenty-eight volumes of expedition journals, “Chūkei sensei nikki”, holding weather, illnesses, gifts from daimyō, disputes with the keepers of his lodgings, and accounts. Always accounts.
His private life unfolds in the shadow of these marches and does not spare him bitterness. His firstborn, Kagetaka – the one of the family testament – dies before his father. His second son is disinherited for a dissolute life. The heir to the Inō house will ultimately be his grandson Tadanori, then in his teens, raised by his daughter Ine. For the ninth expedition, to the Izu Islands in 1815, the seventy-year-old Tadataka no longer has the strength and stays in Edo. For the tenth – the survey of the streets of the capital itself – he sets out once more. It is his last route.
A Death Kept Secret
From 1814 his house in the Hatchōbori district functions as a chizu goyōsho (地図御用所), a map office – a drafting room in which tens of thousands of survey points turn into coastlines. Tadataka works there to the end. He dies on 17 May 1818, at the age of seventy-three, over an unfinished work.
And then his pupils do something unheard of in Japanese bureaucracy: they conceal his death. For three years Inō Tadataka is formally alive, because the work is to be completed under the name of the man who “walked it out.” Only in 1821 does Takahashi Kageyasu, with his team, present the authorities with the complete set: the “Dai-Nihon enkai yochi zenzu” (大日本沿海輿地全図), the complete map of the coastal lands of Great Japan – two hundred and fourteen sheets at a scale of 1:36,000, eight sheets at 1:216,000 and three summary sheets at 1:432,000, plus a volume of survey data from over a thousand astronomical points. Then, and only then, do they announce the mourning. In accordance with his last wish, Tadataka is buried at the temple of Genkū-ji, right beside Yoshitoki. The pupil, older than his master, lies beside him to this day.
The Map’s Afterlife
One might expect the bakufu to proclaim the map a triumph. The opposite happens: the work goes into the castle treasury and disappears. For a map so accurate is also military intelligence – it shows foreigners exactly what they must not be shown. The irony is that this very secrecy will set off the loudest scandal of the age.
In 1828 it comes to light that Takahashi Kageyasu – Yoshitoki’s son, custodian of Tadataka’s legacy and by then one of the shōgunate’s foremost scholars – had handed copies of Inō’s maps to the German physician Philipp Franz von Siebold in exchange for Western books, among them an account of a voyage around the world by Krusenstern. The hunger for knowledge proved stronger than the state’s prohibition. Kageyasu dies in prison, Siebold is expelled from Japan. But the exported copies sail with him to Europe, and it is from them that the West first learns the true shape of the Japanese archipelago. The first reliable map of Japan that Europe ever saw came from under the feet of a retired merchant from Sawara.
From there the story moves at a rush. At the close of the shōgunate the British survey fleet gains access to Inō’s maps and thoroughly improves its own nautical charts of Japanese waters. After the Meiji Restoration the modern state cartography grows directly out of his sheets, and fragments of them serve as late as the early twentieth century. The originals burn in the fire at the imperial palace in 1873; the family’s set of copies is lost in the Great Kantō earthquake of 1923. It seems the great map is gone forever – until, in 2001, two hundred and seven large-scale sheets are found in the Library of Congress in Washington, among them a hundred and forty-eight known until then only from descriptions. Japan recovers its portrait. In 2010 a collection of two thousand three hundred and forty-five objects belonging to Tadataka – maps, journals, letters, instruments – is entered on the list of national treasures. They are kept in the museum in Sawara, a few steps from the house where for thirty-two years he kept his books.
The Second Half
It is easy to make a postcard of this biography: here is a man who, after fifty, fulfilled his dreams. But the postcard lies through simplification. Tadataka discovered nothing in himself in old age – he had carried his curiosity about the heavens and about calculation since childhood, and deferred it for thirty years, because first came obligations: the house, the town, the people dependent on his granaries. He paid them off to the last copper and only then claimed himself. In his life there is no miraculous transformation. There is an order of priorities and discipline.
There is also something that escapes the romantic summaries: the second half of his life grew directly out of the first. Thirty-two years over account books were a training – in patience, precision, daily repetition, respect for the number that must not be fudged. Surveying turned out to be the bookkeeping of terrain. The merchant who noted down every expense became the man who noted down every step. One might try to draw a lesson from our hero’s life. Whoever waits for retirement to “finally start living,” yet in the meantime trains nothing, will not rise after fifty (or, in the twenty-first century, after sixty-five) with a map suddenly in his head. Old age is neither a lottery nor a reward. It is compound interest on everything we paid into ourselves earlier.
And one last thing. Tadataka did not set out to create the greatest work of cartography in his country’s history. He set out to answer one well-posed question – about the length of a single degree (and with it, the size of the Earth). He found the answer as early as the second year of his march. And then he walked on for another fifteen years, because a well-posed question has this quality: it opens the next one. The map of Japan, a national treasure, the pride of museums – all of it a by-product of one retiree’s curiosity.
Sources
1. 渡辺一郎『伊能忠敬の歩いた日本』(Watanabe Ichirō, Inō Tadataka no aruita Nihon, “The Japan That Inō Tadataka Walked”), 1999.
2. 大谷亮吉編『伊能忠敬』(Ōtani Ryōkichi, Inō Tadataka), Iwanami Shoten, 1917; abridged English version: Tadataka Ino: The Japanese Land-Surveyor, 1932.
3. 鈴木純子・渡辺一郎『図説 伊能忠敬の地図を読む』(Suzuki Junko, Watanabe Ichirō, Zusetsu Inō Tadataka no chizu o yomu, “Reading Inō Tadataka’s Maps, Illustrated”), 2010.
4. The Inō Tadataka Museum in Sawara (伊能忠敬記念館) – materials on the national-treasure collection “Inō Tadataka kankei shiryō” (2,345 objects, listed 29 June 2010), including the “Chūkei sensei nikki” journals, city.katori.lg.jp.
5. Tōkyō-to Sokuryō Sekkeigyō Kyōkai (Tokyo Surveying Association), series “Inō Tadataka to Inō-zu” – chronology of the expeditions, survey methods, the fate of the maps, sokuryo.or.jp.
6. Hoshino Yoshihisa, Mapping a Nation: Japan’s Most Famous Cartographer, Inō Tadataka, nippon.com, 2018 (Japanese and English versions).
7. Brock J., Japan’s Most Famous Surveyor: Ino Tadataka and His Iconic 1821 Map of Japan, “Proceedings of the International Cartographic Association,” 2019.
8. Uenishi Katsuya, “Nihon no sokuryōshi: Inō Tadataka” – a detailed chronology of the ten expeditions with Japanese-calendar dates, uenishi.on.coocan.jp.
9. 井上ひさし『四千万歩の男』(Inoue Hisashi, Yonsenmanpo no otoko, “The Man of Forty Million Steps”), Kōdansha – a novel; the source of the popularised, literary count of Tadataka’s steps.
>> SEE ALSO SIMILAR ARTICLES:
With Strength and Humility: How Tamae Watanabe Conquered the World’s Highest Peak Over 70 Years Old
Stay Active and Thriving Even in Your 80s – The Japanese Phenomenon of Radio Taiso
Walking Along a Country Road in Japan, You Encounter the Ancient Dōsojin
"Strong Japanese Women"
see book by the author
of the page
未開 ソビエライ
An enthusiast of Asian culture with a deep appreciation for the diverse philosophies of the world. By education, a psychologist and philologist specializing in Korean studies. At heart, a programmer (primarily for Android) and a passionate technology enthusiast, as well as a practitioner of Zen and mono no aware. In moments of tranquility, adheres to a disciplined lifestyle, firmly believing that perseverance, continuous personal growth, and dedication to one's passions are the wisest paths in life. Author of the book "Strong Women of Japan" (>>see more)
Personal motto:
"The most powerful force in the universe is compound interest." - Albert Einstein (probably)
Mike Soray
(aka Michał Sobieraj)
未開 ソビエライ
An enthusiast of Asian culture with a deep appreciation for the diverse philosophies of the world. By education, a psychologist and philologist specializing in Korean studies. At heart, a programmer (primarily for Android) and a passionate technology enthusiast, as well as a practitioner of Zen and mono no aware. In moments of tranquility, adheres to a disciplined lifestyle, firmly believing that perseverance, continuous personal growth, and dedication to one's passions are the wisest paths in life. Author of the book "Strong Women of Japan" (>>see more)
Personal motto:
"The most powerful force in the universe is compound interest." - Albert Einstein (probably)
Mike Soray
(aka Michał Sobieraj)
Write us...
Ciechanów, Polska
dr.imyon@gmail.com
___________________
inari.smart
Would you like to share your thoughts or feedback about our website or app? Leave us a message, and we’ll get back to you quickly. We value your perspective!