License, verbatimPD
The National Gallery of Art: open access image with no usage restrictions under the NGA's open access policy (openaccess=1 in the Gallery's published_images dataset).
Nicolas Poussin. Modello for a Ceiling: Diana and the Dead Endymion, the Judgment of Paris, and the Death of Adonis, 1640/1642 (?). National Gallery of Art, Washington.