Nakane Genkei (中根元圭)
Genkei NAKANE (1662 - October 9, 1733) was a wasanka (mathematician) and tenmonka (astronomer) in the middle of the Edo period. He excelled in kangaku (study of the Chinese classics) and musical theory. His first name was Akira. His common name was Joemon. He chose Genkei for his azana (adult male's nickname). He chose Risshu for his go (pen name).
He was born in Azai County, Omi Province. As he had lived in Hakusan-cho, Kyoto, he was called Hakusan sensei (Sir Hakusan), and he worked as a government official in Ginza (an organization in charge of casting and appraising of silver during the Edo period). He was originally a disciple of Yoshizane TANAKA, and from an early age he wrote books such as "Shinsenkorekibinran," "Sanseizokukai," "Jujirekizukaihakki," and so on.
In 1721 (or 1717 in another opinion), he was invited to Edo on the recommendation of Katahiro TAKEBE, and suggested to Yoshimune TOKUGAWA that he allow people to import only the useful foreign books such as books on astronomy. While this episode may have a contradiction between the years, it is said to have been a trigger to loosen the order to ban the import of the foreign books in 1720. In 1726, he was ordered to convert into the Japanese-style reading and translate "Rekisanzensho," and in 1733, when he was 72 years old, he completed the task, but he died in the same year.
He was also excellent in musical theory, and considered the relationship between the scales of the gagaku (ancient Japanese court dance and music) and the worldly music that had been developing individually. What is more, he wrote "Ritsugen hakki" featuring the equal temperament of 12 degrees which was resulted from the expansion of 1 octave into 12th root.