License, verbatimCC0
The Metropolitan Museum of Art: Open Access, Creative Commons Zero (CC0). Flagged isPublicDomain=true in the museum's own record.
Stefano della Bella. Plate 6: Two studies of children, from "Collection of various doodles and etching proofs" (Recueil de divers griffonnements et preuves d'eauforte), ca. 1646. The Metropolitan Museum of Art.