In 1934, Purdue University physicists said the whole body may be kept cool during the hottest weather by a developed miniature refrigerator that straps to the wrist in the manner of a watch.

The refrigerator was somewhat larger than a wrist watch and encloses a pellet of dry ice–solid carbon dioxide. As the dry ice evaporates, it forms an invisible gas. Escaping from the case, the gas has the same effect as cold water poured over the wrists. It lowers the temperature of the blood in the arteries and this cooled blood is carried to every part of the body.