What did the steam-powered two-wheelers around 1867 prove conceptually, despite their impracticality?

Answer

That self-propulsion on two wheels was physically possible

The early steam-powered attempts around 1867, although described as unwieldy and heavy contraptions, served a crucial conceptual role in the history of the motorcycle. Their significance rests on the fact that they demonstrated the fundamental possibility of achieving self-propulsion on a two-wheeled vehicle using an onboard engine. Although steam lacked the efficiency and portability of future gasoline engines, these initial forays validated the basic physics required for motorized personal transport on two wheels.

What did the steam-powered two-wheelers around 1867 prove conceptually, despite their impracticality?
inventionVehiclefirstYearmotorcycle