Muramatsu Shigekiyo

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Muramatsu Shigekiyo (1608–1695) was a Japanese mathematician and curator in the Edo period. He was the first to estimate the volume of a sphere by slicing it into very thin pieces. He also used inscribed and circumscribed polygons to approximate the circumference of a circle and thus pi. Using a 32,768‑sided polygon, he calculated its perimeter as 3.141592648... He published his value of pi to 22 decimal places in his 1663 book Sanso, but only eight digits were correct. In 1681, Seki Takakazu used the same method with a 131,072‑sided polygon and obtained pi correct to 11 decimal places.