From Giorgio Vasari, Lives of the Most Eminent Painters, Sculptors and Architects (1568)—
He [Leonardo da Vinci] would often dry and purge the guts of a wether [a gelded male sheep] and make them so small that they might be held in the palm of the hand. In another room he kept a pair of [black]smith's bellows, and with these he would blow out one of the guts until it filled the room, which was a large one, forcing anyone there to take refuge in a corner.
