Louis Albert Necker, (April 10, 1786 – November 20, 1861), was a Swiss crystallographer. He is best remembered for devising the optical illusion now known as the Necker cube. April 10 is the 100th day of the year in the Gregorian calendar (101st in leap years). ... 1786 was a common year starting on Sunday (see link for calendar). ... November 20 is the 324th day of the year (325th in leap years) in the Gregorian calendar. ... 1861 (MDCCCLXI) was a common year starting on Tuesday (link with display the full calendar) of the Gregorian calendar (or a common year starting on Thursday of the Julian calendar) // January 1 - Benito Juárez captures Mexico City January 2 - Friedrich Wilhelm IV of Prussia dies and is succeeded by... Crystallography (from the Greek words crystallon = cold drop / frozen drop, with its meaning extending to all solids with some degree of transparency, and graphein = write) is the experimental science of determining the arrangement of atoms in solids. ... An optical illusion is always characterized by visually perceived images that, at least in common sense terms, are deceptive or misleading. ... The Necker Cube is an optical illusion first published in 1832 by Swiss crystallographer Louis Albert Necker. ...