The 1970 World Expo in Osaka, Japan had the theme of "Progress and Harmony for Mankind," and drew record numbers. Some 64 million people from 77 countries attended.

One of the more unusual objects on display was this Sanyo Ultrasonic Bath.

The demonstration model would climb into the six-foot-tall machine via ladder, then enter the chamber, with their head sticking out of the top. They'd set the water temperature, then the machine would start spraying them with jets of warm water, like the pre-wash cycle at a car wash.

After five minutes of that, the machine would then fill the chamber with hot water for a three-minute ultrasonic bath. This was followed by a two-minute hot rinse cycle. Next, the chamber would drain and the user was blasted with warm air to dry off. They were additionally exposed to both infrared and ultraviolet light to kill germs. All in all, it was a 15-minute cycle.

Today the prototype is stored in the Panasonic Museum. (The company acquired Sanyo in 2009.)

Unsurprisingly this never made production. However, it has inspired Japan's Science Group, who we wrote about here, to bring back the concept for 2025, when Osaka will again host a World Expo. Science Group's prototype, shown below, is intended to have applications in the healthcare sector.