The Ambassadors by Hans Holbein the Younger

Two young Frenchmen, Jean de Dinteville and Georges de Selve, pose in 1533 among brand-new, expensive scientific instruments. Holbein packed the shelves between them with globes, sundials, a Lutheran hymnbook and a lute with a broken string, then stretched a skull across the floor that only snaps into shape when you look from the right-hand side, a reminder of how it all ends.

Hans Holbein the Younger, 1533. Museum-grade giclee print of the public-domain original.