William Shanks

[2] Nevertheless, Shanks's approximation was the longest expansion of π until the advent of the digital electronic computer in the 1940s.

After his marriage in 1846, Shanks earned his living by owning a boarding school at Houghton-le-Spring, which left him enough time to spend on his hobby of calculating mathematical constants.

He published a table of primes (and the periods of their reciprocals) up to 110,000 and found the natural logarithms of 2, 3, 5 and 10 to 137 places.

Given the nature of Machin's formula, the error propagated back to the 528th decimal place, leaving only the first 527 digits correct once again.

[4] In April 1873, twenty years later, Shanks expanded his calculation to 707 decimal places.