Here are a few more things that you might not Know
Before Mopeds there where Cycle Motors
These where basically bicycles with 50cc (or smaller) power packs bolted on, here are a few examples.
The BSA Winged Wheel
This was a 35cc power pack that replaced the rear wheel
This was another rear wheel replacement power pack this time 32cc
The Vincent Firefly
This 48cc package bolted under the frame and drove the rear Wheel using a serrated roller