torture wheel The Breaking  Wheel.

The breaking wheel was also known as a great dishonor, and appeared in several expressions as such. In Dutch, there is the expression opgroeien voor galg en rad, "to grow up for the gallows and wheel," meaning to come to no good. The Dutch expression ik ben geradbraakt, literally "I have been broken on the wheel", and the German expression sich gerädert fühlen, "to feel wheeled," are used to describe mental exhaustion or hard attempts to remember things.

Perhaps Bosch was symbolically making reference to the crucifixion of Jesus.