The Virgin and Child with Saint Anne (cartoon)

The Virgin and Child with Saint Anne is a cartoon said to have been created by Leonardo da Vinci as part of his "Virgin and Child with Saint Anne" project, and now considered lost. It is known from a letter written on April 3, 1501, by Fra Pietro Novellara, Isabella d'Este's envoy to the painter.

Source: Wikipedia — The Virgin and Child with Saint Anne (cartoon) (CC BY-SA 4.0)