On various occasions I have written about "literary madmen," but they are not merely a fixation of mine. I find that reflecting upon outlandish theories that were taken seriously for a long time teaches one to distrust many ideas that are accorded full credence in the media, and even in some scientific circles.
I remember first reading about and being fascinated by the concave hollow Earth theory in Omni magazine. Martin Gardner has discussed it elsewhere. From Wikipedia:
Martin Gardner notes that "most mathematicians believe that an inside-out universe, with properly adjusted physical laws, is empirically irrefutable". However, Gardner rejects the concave hollow Earth theory, not as disproven, but instead entirely on the basis of Occam's Razor.