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 as a "classic crank book." [4]

Selected works

  • Heisel, Carl Theodore (1934). Mathematical and geometrical demonstrations, disproving numerous theorems, problems, postulates, corolleries, axioms naturally growing out of the extraordinary discoveries of a lacking link (2d. ed.). Cleveland.


  1. ^ "Carl Theodore Heisel (1852–1937)". Find a Grave. Retrieved 31 May 2019.
  2. ^ "WorldCat Listing". Retrieved 16 May 2019.
  3. ^ Simanek, Donald E. "Carl Theodore Heisel Squares the Circle". Retrieved 23 May 2019.
  4. ^ Paul R. Halmos (1970). "How to Write Mathematics". L'Enseignement mathématique. 16 (2): 123–152.How to Write Mathematics