This Monowheel from 1931
This monowheel or uniwheel was a one/wheeled single/track mode of transportation not unlike a unicycle. But instead of sitting above the wheel like a unicycle, the rider sat within the wheel or next to it. But most of them have the same principle as a bicycle in that the rider has to pedal their way, but this one looks like it has a motorcycle engine and a steering wheel. That’s pretty inventive considering that this image was taken in 1931 when mechanical gadgets were still in their infancy.