Andy Warhol:

“After Billy finished working on the galleys of a... he went into his darkroom and didn’t come out... In the mornings we would find take-out containers and yogurt cups in the trash, but we never knew whether he went out himself at night to get food or whether some of his friends brought it in to him... but then one day Lou Reed came by and spent three whole hours in the darkroom with Billy. Lou came out regretting that he had given him three Alice Bailey books on witchcraft. Billy had shaved his head completely because he believed the hairs were growing in, not out - and was only eating whole-wheat wafers and rice crackers now - following the white magic book that shows you how to rebuild your cell structure.” (POP290)

People who hung out at the Factory could also hear Billy talking to himself in the dark room in two different voices. (ibid)