Carl Theodore Heisel (1852–1937) was a mathematical

crank Crank may refer to: Mechanisms * Crank (mechanism), in mechanical engineering, a bent portion of an axle or shaft, or an arm keyed at right angles to the end of a shaft, by which motion is imparted to or received from it * Crankset, the componen ...

who wrote several books in the 1930s challenging accepted mathematical truths. Among his claims is that he found a way to

square the circle Squaring the circle is a problem in geometry first proposed in Greek mathematics. It is the challenge of constructing a square with the area of a given circle by using only a finite number of steps with a compass and straightedge. The diffic ...

. He is credited with 24 works in 62 publications. 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.

Paul Halmos Paul Richard Halmos (; 3 March 1916 – 2 October 2006) was a Kingdom of Hungary, Hungarian-born United States, American mathematician and probabilist who made fundamental advances in the areas of mathematical logic, probability theory, operat ...

referred to one of Heisel's works as a "classic crank book." �
How to Write Mathematics
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Selected works

References

{{DEFAULTSORT:Heisel, Carl Theodore Pseudomathematics 1852 births 1937 deaths