Staircase Group (Portrait of Raphaelle Peale and Titian Ramsay Peale I), 1795) Charles Willson Peale.
Via Books and Art
Peale painted this life size portrait to be a trompe l'oeil and fool the eye into thinking it was real. To that end, he installed the painting in his studio inside a door frame with a step in front of it. It must have fooled many people.