French mathematician, physicist, inventor, philosopher, and Catholic writer Blaise Pascal was born #OTD in 1623.
One of his most famous contributions in Mathematics is the Pascal's Theorem. Along with Pierre de Fermat, Pascal is credited with founding probability theory. He also made significant contributions to the study of binomial coefficients, which led to the formation of Pascal's Triangle.
Books by Blaise Pascal at PG:
https://www.gutenberg.org/ebooks/author/7913