In his book The Long Trip: A Prehistory of Psychedelia (Amazon US and Amazon UK), Paul Devereux recounts the theory that imagery and folklore about Santa Claus may have been influenced by the shamanic history surrounding the psychedelic mushroom, Amanita muscaria:

According to Rogan Taylor, perhaps the most amusing hint of the memory of amanita-based shamanism may well be enshrined, perhaps by accident, in the popular contemporary image of Santa Claus. The figure of Father Christmas evolved over centuries out of pagan traditions, but the modern image of Santa owes most to the elements cobbled together in the 1820s by Professor Clement Clark Moore of Albany, New York, along with illustrators Thomas Nast and Moritz von Schwind, both of Germanic descent. Taylor feels that some traditional elements got pasted into their version, perhaps from the professor’s wide reading, or from the illustrators’ Old World links – or both. He points out that Santa’s robe of red edged with white are the colours of Amanita muscaria, that the idea of Santa clambering down the chimney evokes the entry via the smoke hole into Siberian yurts during winter. Moreover, the reindeers that pull the sleigh can be seen to link to the reindeer-herder tribes who took the magic mushroom. And the magic flight of Santa Claus through the midwinter night sky is a superb expression of the basis of all shamanism – ecstasy, or the flight of the spirit.

Film-maker and animator Matthew Salton has now put these ideas into video format, in which he discusses the theory along with input from Carl Ruck, a classicist at Boston University who has previously investigated ancient psychedelic use, and Lawrence Millman, a writer and mycologist: