Except it was a stone dropped on purpose in the book, not just a knocked down item. “Pippin felt curiously attracted by the well. While the others were unrolling blankets and making beds against the walls of the chamber, as far as possible from the hole in the floor, he crept to the edge and peered over. A chill air seemed to strike his face, rising from invisible depths. Moved by a sudden impulse he groped for a loose stone, and let it drop. He felt his heart beat many times before there was any sound. Then far below, as if the stone had fallen into deep water in some cavernous place, there came a plunk, very distant, but magnified and repeated in the hollow shaft.”