The Soothsayer

Poggio Bracciolini, Facetiae CLXIV (In Which Gonella, the Jester, Wins a Wager; tr. Anonymous):

It is told of Gonella, the clever jester, that he wagered with a man from Ferrara that he would make a soothsayer of him.

He took his companion to bed with him and, breaking wind softly, instructed him to stick his head under the covers. The other obeyed, but immediately withdrew, offended by the foul odor.

“It appears to me that you have farted,” he said. Upon which Gonella cried: “Correct! I win the bet, for you are already a soothsayer!”