Sometimes I'll pick up the "heart of the jungle" fossil on my bookshelf, or pull out my old field notebooks from my desk drawer, warped by Amazonian rains and the river's steam, the scent of the jungle still on their pages. I do this to remind myself that fiction does not have a monopoly on the unbelievable.
Separating fact and fiction in Inca history is impossible, because virtually all the sources available are Spanish accounts of stories that had already been vetted by the Inca emperors to highlight their own heroic roles. Imagine a history of modern Iraq written by Dick Cheney and based on authorized biographies of Sadam Hussein published in Arabic, and you'll get some idea of what historians face.