Some people call Leonard Euler “Analysis Incarnate.” He is known for various works in number theory, the sum of 1/n^2, the development of the concept of functions with D’Alembert. Euler could calculate large calculations entirely in his head. He liked children and had many of them. Unfortunately, Euler slowly went blind, and he was completely blind by the time he was 70. His blindness did not hinder his mathematical insight, but rather, it increased after he became blind.
Becca Hirsbrunner photographed this fabulously constructed Z proportions letter. Interestingly, every element but the diagonal bar can be rationalized.