The idea of World as Myth was created by science fiction writer Robert A. Heinlein in his book The Number of the Beast. According to this idea, myths and fictional worlds exist as an almost infinite number of universes which are parallel to our own. In this multiverse, Heinlein's Future History timeline is merely a few of the vast number of constituent universes that comprise the World as Myth. In The Number of the Beast, four characters traveled to multiple fictional universes, including several of Heinlein's own. Others included E.E. Doc Smith's Lensman series, L. Frank Baum's Oz books, and Lewis Carroll's Alice in Wonderland.