Recently I learned about another example, possibly one of the most impressive yet. R. Webster Kehr is a Mormon and ex-Marine who
- thinks that the naturals and the reals are the same size, even though he admits there is no bijection between them. He also describes himself as the author of many mathematical papers, although oddly enough, MathSciNet doesn't list a single one.
- subscribes to cancer quackery
You have to work pretty hard to be so deluded in so many fields simultaneously.