Listaholic has an interesting (though gruesome) article about the 12 most horrifying torture devices in history.
This one to the left is the Judas Chair [wiki]:
The Spanish Inquisition was said to have made use of, among other things, the Judas Chair, also known as the Judas Cradle. Victims were hoisted up by rope or chain and then made to sit on the pointed tip of the pyramid shaped device. You get the picture.