Cartesian Addressing System in the Ancient City

In 1979, a bronze plate of an epitaph was discovered from an old tomb on a hill in the eastern suburbs of Nara City. From the words on the plate, it became clear that the buried person was Ô-no-Yasumaro, a man from the 7th to the 8th century. This was big news because he was famous for compiling Japan's first history, Kojiki. The epitaph states the following.

Ô-no-Ason-Yasumaro, a resident (in the city-block) of the fourth Jô (row) and fourth Bô (column) in the Left City (of the Capital), at the junior fourth-rank lower in the Court and the fifth Order of Merit, died on the 6th day, 7th month of the year of Gui-Hai [the 60th year of the Chinese zodiac cycle] (August 11, 723 AD by the Julian calendar).

(Inscribed) on the 15th day, 12th month, 7th year of the Yôrô era (January 15, 724 AD by the Julian calendar).

This description informs us that, in the ancient capital of Nara, each city-block was specified by row and column numbers in a way somewhat similar to the Cartesian coordinate system. In China's capital Chang-an, after which Japan modeled its capital, such an addressing system seems not to have been adopted. Instead, the Chinese named each city-block in the capital.

The epitaph of Ô-no-Yasumaro.

The following illustration shows how a city-block was specified in ancient Nara.

By Noboru Ogata, Kyoto University

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