Arima Yoriyuki

Arima Yoriyuki (有馬 頼徸) was a Japanese mathematician of the Edo period. He was the lord of Kurume Domain.

He approximated the value of $\pi$ and its square, $$\pi^2$$. In 1766, he found the following rational approximation of $$\pi$$, correct to 29 digits:


 * $$\pi\approx\frac{428224593349304}{136308121570117}=3.14159265358979323846264338327(569...).$$