I bought an old Magnavox tv with built in Pong, but it was missing the controllers. To play games, my brother and I would shove speaker wires into the ports and hold the bare wires with our hands.
By staying very still and very carefully pinching one wire in each hand, tips of fingers touching, we could control the resistance in the range needed to start and control the game. So much as a twitch or turning your head would cause the pong paddle to go off the screen.
Holding that still and staring at the tv, it looked like we were controlling it with our minds.
After a couple days, the TV died. But $18 well spent.