The first poetical tale in Thomas Moore's Lalla Rookh.
The Veiled Prophet of Khorassan was Hakim ben Allah, surnamed the Veiled (Mokanna), founder of an Arabic sect in the eighth century. Having lost an eye, and being otherwise disfigured in battle, he wore a veil to conceal his face, but his followers said it was done to screen his dazzling brightness. He assumed to be a god, and maintained that he had been Adam, Noah, and other representative men. When encompassed by Sultan Mahadi, he first poisoned all his followers at a banquet, and then threw himself into a burning acid, which wholly destroyed his body.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894