Years ago an acquaintance built this 'perpetual motion machine', which was ran by what I call a 60 Hz Crystal radio. Hidden in the base was a large coil, diode (bridge?) and a capacitor to store the energy. Also a small reed switch and a small coil. All hidden in the wooden base. The machine was a large (18" - 24") plastic wheel disc with 4 magnets located 90deg apart along the edge. Mounted along side the wheel was a plate with magnets attached. This was supposedly what made the motor run.
One magnet on the edge of the wheel disc was reversed to close the reed switch as it came by and discharge the cap through the small coil to add power to the wheel every revolution. The small power coil was mounted very close the magnets by having the hollow wooden base very thin for the reed switch and small coil. This thing rotated at probably 20 - 30 rpm and would run forever with no apparent power.
I suspected a hidden battery, coil and switch. Only when you removed the green felt and removed six screws did the bottom cover come off and could you see that he was drawing power from the 60 Hz fields in his house. Not much, but enough to overcome friction losses. The 'antenna' coil was many turns fitted into a groove close to the edge of the base. The other items were in a blind hole under the wheel.
I lost contact with him many years ago and I have never been able to build an LC circuit, or a crystal radio circuit optimized to get the most out of the field. This thing was nice looking with a cherry wood base and it just set on a table in a corner and fooled many people.