What to put in a Japanese puzzle box?

A Japanese puzzle box, or himitsu-bako, can hold a variety of items, such as small trinkets, jewelry, or notes. The contents should be meaningful or personal, enhancing the experience of unlocking the box. Additionally, you can include items that reflect Japanese culture, like origami or small art pieces. Just ensure the items fit comfortably within the box and are not too heavy, as this could affect the mechanics of the puzzle.