Nancy Drew: The Haunting of Castle Malloy

To light the lantern in the library, rearrange the discs so that everything is in the same order on the right pole as it is stacked on currently on the left pole. This would be easy, but you can't stack a large disc on top of a disc with a smaller diameter. The trick is to move the largest disc to the right pole and the next largest disc to the middle pole. This means you move the discs with the smallest diameters far more than the wide pieces at the bottom.