Between the 1860s and 1930s, the monowheel (also known as the monocycle) was often suggested as a serious new form of transportation.
Several inventors came up with their own versions of the monowheel, some human-powered, some electric, some with gas motors, all operating on the same basic principle: the driver sits within a small inner ring, which is connected to the main outer ring. Presses against the wheel, allowing the vehicle to roll forward while the driver remains level.
In 1869, a French inventor created the first known monowheel, but it actually had two wheels. It was a huge wheel with a seat inside. There was another small wheel under the seat. The rider pedals to move the smaller wheel, which in turn turns the larger wheel.
Even at the time, the monowheel was recognized as a difficult mode of transportation and was described as "impractical for ordinary humans".