Watch closely Westley is fighting Inigo atop the cliffs of insanity. Towards the end of the battle after they have already switched from right to left hands they both go on a smaller bunch of rocks. Inigo walks/climbs up the rocks and turns around the face Westley. Instead of doing the same as Inigo he decides to float up on top of the rocks. He is supposed to be jumping but he really appears to be jumping from a spring or trampoline.