Can Failing to Check Sources Give Rise to Monsters? The Iconographical History of a Paradigmatic Case

In the early fourteenth-century chronicle by Giovanni Villani there is a singular report of a monstrous birth. The little double monster was depicted in a sandstone panel that was exposed in the front of the Santa Maria della Scala hospital in Florence. This essay tries to prove how failing to check sources gives rise to monsters by following the extraordinary iconographical history of this particular image of conjoined twins.