Arima Yoriyuki

Arima Yoriyuki (有馬 頼徸, December 31, 1714 – December 16, 1783) was a Japanese mathematician of the Edo period. He was the lord of Kurume Domain and approximated the value of $\pi$ and its square, $\pi^2$. In 1766, he found the following rational approximation of pi, correct to 29 digits:^[1][2]

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

References

1. "Collection of approximations for $\pi$". Retrieved 2008-04-04.
2. Hardy, G. H.; E. M. Wright (1978). An Introduction to the Theory of Numbers. Oxford Science Publications.