License, verbatimCC0
The Metropolitan Museum of Art: Open Access, Creative Commons Zero (CC0). Flagged isPublicDomain=true in the museum's own record.
Leonardo da Vinci. Compositional Sketches for the Virgin Adoring the Christ Child, with and without the Infant St. John the Baptist; Diagram of a Perspectival Projection (recto); Slight Doodles (verso), 1480–85. The Metropolitan Museum of Art.