I have a magic rectangle. One side of it is metal, the other glass. Inside it are crystals of exceptional fineness, metal etched into intricate patterns, and traces of many exotic elements, all from different faraway lands. Symbols appear on the glass, and if touched in the right order, many wondrous and terrible things can happen. Just as often, they do not, and I have to spend an hour working out which part of the ritual I messed up.