The more than fifty woodcut illustrations in the text include celestial charts, phases of the Moon, and a map of the Eastern Hemisphere. The work is divided into five volumes.
 
The first volume presents Iguchi’s theory of astronomy and planetary motion and his observations of comets; he discusses the possibility of comets reappearing some years before Edmond Halley.

The next three volumes are largely concerned with the reform of the Chinese lunisolar Hsuan-ming calendar, adapted in Japan in 862. The Hsuan-Ming calendar had become increasingly inaccurate in the prediction of solar and lunar eclipses. In early Japan, knowledge of astronomy and the ability to predict eclipses were considered by the imperial court to be of the greatest importance, and calendar reform was therefore a priority.

The end of the fourth volume deals with the ‘yun qi lun’ theory which is one of the theoretical foundations of Chinese medicine and acupuncture.

The fifth volume is devoted to calculating the positions of heavenly bodies, including woodcuts showing a geocentric universe and the Chinese constellations.

Although all five volumes mention the study of mathematical astronomy, the first volume has circular star maps and the second has figures of the lunar lodges. Most of the stars are shown as black circles, but those of the lunar lodges and other notable stars in the circular star map are shown as white circles, as are the determinative stars in the figures of the lunar lodges.

The map of the eastern hemisphere shows Japan in the centre, an illustration of an armillary sphere with dragon-shaped legs, and a diagram of the nine-sphere universe reproduced from the Chinese edition of Matteo Ricci’s ‘A Profound Demonstration of the Two Spheres’ (1603).

However, Iguchi’s map shows a very interesting particularity. In the southeast of Japan, the map is illustrated with two imaginary islands: ‘Kinshima’, the gold island, and ‘Ginshima’, the silver island. The source for this cartographical anomaly is not clear, as extensive explorations of the Pacific by Dutch and Spanish navigators in the sixteenth and seventeenth centuries failed to find any evidence of them.

Iguchi Tsunenori was widely influenced by the research of his colleague, Shibukawa Harumi (1639–1751), who had carried out the first astronomical observations in the country in 1669. Harumi had studied the Moon, Sun, and motions of the planets as well as eclipses, and had used those new data to draw up the first calendar in Japan, the ‘Jokyo’. While Iguchi’s work is based on Harumi’s raw data, it is also influenced by advances in Western astronomy made by Johann Adam Schall von Bell (1591–1666), and Ferdinand Verbiest (1623–1688).

This straightforward first edition of the first astronomical book to be published in Japan illustrates the convergence of European and Chinese astronomy. Iguchi Tsunenori's work combines and critiques Chinese, Buddhist, and European sources, including Shibukawa Harumi’s ‘Jokyo’ the first Japanese calendar. While Iguchi’s work is based on Harumi’s raw data it is also influenced by advances in Western astronomy made by Johann Adam Schall von Bell (1591–1666), and Ferdinand Verbiest (1623–1688). With more than fifty woodcut illustrations, the text includes celestial charts, phases of the moon, and a map of the Eastern Hemisphere.

There is enough evidence to suggest that celestial maps in ancient and medieval Japan were of Chinese derivation, brought to, or copied in Japan, in manuscript form. 

The most influential of these works, in the early Edo period (1600-1868), were Chen Yuanjing's ‘Shilin guang ji- “Records of many things” (c1250), Wang Qi's ‘Sancai tuhui’ – “Illustrated compendium of the three powers [Heaven, Earth, and man]” (completed 1607, printed 1609), and You Yi's ‘Tianjing huowen’ –“Questions and answers on astronomy” (1672). 

Iguchi Tsunenori's work combines and critiques Chinese, Buddhist, and European sources: he comments that the Buddhists still insist on spurious ancient ideas, while Confucians have compromised their theories to fit with a more modern theory of a spherical Earth.

An exceptionally fine, and unsophisticated example of the first edition of the first astronomical book to be published in Japan, it illustrates the convergence of European and Chinese astronomy.



Original blue paper wrappers, manuscript paper labels, sewn as issued; modern cloth chemise.



5 parts bound in 6 volumes. Octavo; 32, 31, 37, 31, 33 and 54 leaves, Japanese rice paper; 50 woodcuts, including 4 double-page plates, including 14 heightened with contemporary hand-colour.

Explanation of Astronomy by Means of Figures

Tenmon Zukai

Iguchi Tsunenori, after: Shibukawa Harumi, Johann Adam Schall von Bell, Ferdinand Verbiest, and Matteo Ricci

