Material: 2 glasses of water with black border, chalk sticks.
Two glasses full of water, a black marker that draws on the edge of the glasses a black line, a white chalk to trace two circles on the floor.
All for a bet of one euro.
The stakes? Guess the water level in the glasses after a walk.
Some drops fall down the road, and at the end of the path the water level is above or below on black line. We will never know because the glasses slip from the hands and break when in contact with the ground.