License, verbatimCC0
The Metropolitan Museum of Art: Open Access, Creative Commons Zero (CC0). Flagged isPublicDomain=true in the museum's own record.
Gilles Rousselet. Dialectic: a young woman standing in a decorated interior and touching her right index finger to her left middle finger in a counting gesture, at her feet is a toad seated on a stack of books, from "The liberal arts" (Les arts liberaux), 1633–35. The Metropolitan Museum of Art.