A puzzle from Henry Ernest Dudeney:

Here is a simple question that will require just a few moments’ thought to get an exact answer. I have a piece of cheese in the shape of a cube. How am I to cut it in two pieces with one straight cut of the knife so that the two new surfaces produced by the cut shall each be a perfect hexagon? Of course, if cut in the direction of the dotted line the surfaces would be squares. Now produce hexagons.