the secret revealed!
Diagrams of Humor & the Center of Levity, 1878 via @ptak
The images describe the concepts of force, gravity and momentum using vectors.
The Mobius strip is a surface with one side and one boundary. It was discovered indipendently by August Ferdinand Möbius and Johann Benedict Listing in 1858.
Read also: How to cook a Mobius steak!
Donatello, Raffael, Leonardo, and Michelangelo - the ORIGINAL Ninja Turtles!