Prayer Wheel is an early work exploring the buildup of momentum in a radial system (radial inertia in the colloquial and not the physics sense). It is a work better felt than seen. It allows you to play with two rocks, each weighing about 400 lbs, that spin around a center shaft with very little friction. What people find is that it is a lot easier to put energy into the system to get the rocks spinning than it is to stop them. This leads to the often amusing moment like watching a big guy trying to dead stop the work and ending up being involuntarily skipped backwards accompanied by grunts of efforts and surprise. Children, on the other hand, seem to often have a very intuitive grasp of the work and love getting it in motion, then riding one of the rocks around.