The Ambassadors by Holbein (on the left) at the National Gallery. This painting is famous for multiple embedded images, one being a carving of Jesus on a crucifix, half hidden behind a curtain at the top left. Another, more obvious is the odd slanted image at the bottom which is an example of anamorphosis which is a distorted image that requires the viewer to occupy a specific vantage point, use special devices, or both to view a recognizable image. To the right is the undistorted version of that image – a skull.