License, verbatimCC0
The Metropolitan Museum of Art: Open Access, Creative Commons Zero (CC0). Flagged isPublicDomain=true in the museum's own record.
Etienne DuPérac. Half-Section of the Model of the Attic and Dome of Saint Peter's Basilica as Conceived by Michelangelo (recto); Detail Studies Relating to the Plan, Section, and Elevation of the Dome of Saint Peter's Basilica (verso)., 1551, 1558–69. The Metropolitan Museum of Art.