Funa-dansu: Traditionally used by merchants to safeguard important valuables while traveling at sea. Many of these chests were so well made, they were rumored to be water-tight in case the ship encountered trouble.
Float on water and Karakuri chest
“Ship Chests” and their Tricks
One of the more interesting tansu ever to be made in Japan was the funa-dansu (ship chest) which was in fact an early type of safe. Funa-dansu were frequently used to transport large amounts of money on the kitamae-bune ships, which plied the seas carrying goods from one part of Japan to the other. The boxes had to be strong and they had to be made so that only the owner could gain access. Moreover the inner compartment needed to be watertight to keep the contents safe should the ship sink. For this reason the inner compartments were always made from paulownia, while the outsides were of beautifully grained zelkova. A funa-dansu is typically further encased in intricately detailed metal fittings, which not only add strength but beauty.
In any one of funa-dansu one can find 300 different wooden pieces and 300 to 500 hand-forged nails. In addition, each comes with five different keys.