Carl Theodore Heisel
From Wikipedia, the free encyclopedia
Carl Theodore Heisel (1852–1937)[1] was a mathematical crank who wrote several books in the 1930s challenging accepted mathematical truths. Among his claims is that he found a way to square the circle. He is credited with 24 works in 62 publications.[2] Heisel did not charge money for his books; he gave thousands of them away for free. Because of this, they are available at many libraries and universities. Heisel's books have historic and monetary value.[3] Paul Halmos referred to one of Heisel's works (a book claiming to have accomplished the impossible task of squaring the circle) as a "classic crank book."[4]
