Back when I was a kid there was an episode of "The Woodwright's Shop", where he talked about creating a wood box with no seams containing a coin. The trick was

Back when I was a kid there was an episode of "The Woodwright's Shop", where he talked about creating a wood box with no seams containing a coin. The trick was to drill several holes in a tree that you'll eventually cut down, and fill them with coins. Wait five or ten years for the tree to grow wood around them, then cut the tree down and carve out the boxes from the outside, leaving a hole to view the coin.