Exhibit on display in Stanislaw Lem Garden of Experiences, a branch of the Museum of Municipal Engineering in Krakow.
Description written by Michał Urban
Grab the handle connected to the long belt wrapped around the metal spool. The spool is free to roll along a level track. Notice that when the angle of the belt to the track is steep, like when you pull the belt upwards, towards your head, the spool rolls away from you. But when you pull the belt at a shallow angle, toward your knees and keeping it level with the track, the spool moves in your direction. You can even try to find an intermediate angle, between the two aforementioned situations. The spool will then move toward you without rolling, it will remain motionless relative to the belt.