German mathematician Ludolph van Ceulen spent the majority of his life deriving the digits of pi(π). In 1610 he died of exhaustion after deriving the 35th decimal.
The 35 digits are engraved in his tombstone.
π ≈ 3.14159265358979323846264338327950288
As an aside, we currently know pi to over 2.5 trillion places.