Infinite Powers: The Story of Calculus - The Language of the Universe

by Steven H. Strogatz

What I’m trying to say is that his calculation of π was heroic, both logically and arithmetically. By using a 96-gon inside the circle and a 96-gon outside the circle, he ultimately proved that π is greater than 3 + 10/71 and less than 3 + 10/70.