Related subject:
Friar Cipolla, after losing a "feather from Angel Gabrial" (actually a parrot's feather), convinces the idiotic mass that some bits of coal were left over from roasting of Saint Lawrence, and said--
"[...] I must tell you that all those who are marked with the sign of the cross by these coals may rest assured that for a whole year they will never be touched by fire without getting burnt."
the mass, after hearing these exact words, were relieved and believed the exact opposite of Friar Cipolla's words.
--From Boccaccio's Decameron