License, verbatimCC0
The Metropolitan Museum of Art: Open Access, Creative Commons Zero (CC0). Flagged isPublicDomain=true in the museum's own record.
Antonio Tempesta. Plate 100: Apollo Killing the Serpent Attacking Opheus's Head (Serpens Orphei caput dilaniaturus in saxum ab Apolline convertitur), from Ovid's 'Metamorphoses', 1606. The Metropolitan Museum of Art.