Salvator Mundi

A solid crystal sphere held in front of fabric should refract and invert the image of the fabric behind it. Leonardo's doesn't. The cloth shows through undistorted, as if the orb were a soap bubble. He knew optics well enough to paint refraction correctly — there are diagrams of it in his notebooks. He chose not to. The painting is the most expensive ever sold and the choice has been argued about for fifteen years. Now in a private collection.