Ah, I don’t mean to try to top you, but that reminds me of three something-for-nothing “inventions” of mine.
When I was very young, I reasoned that it would be very easy to have a vehicle run on a level surface with no fuel (and nothing external to push or pull it.).
Picture a car coasting down an incline. Now forget about the surface it rides down, and just imagine the car out of its context. It has a down-in-front slant, right?
Well, then, all you have to do is build a car with the back wheels higher than the front, to create “slantness” and you have your fuel-free car. (This was at least a decade before it became common for ordinary road cars to be built-up in back.)
Later, at age 10, at least, I thought you could have a spaceship featuring two large magnets mounted inside. The larger would atrqact the smaller more than vice-versa. (WRONG!) The space ship would move in the direction of the larger magnet. No fuel or outside impetus would be necessary. Another Perpetual Motion dream. A bright classmate, although mostly in love with drawing, had the acumen to know why such could never work. But whan he tried to expalin it to me, the fresh terminology he used simply baffled me.)
I wasn’t one to give up. A huge book, devoted to teaching kids science, showed an example of a failed PM device. A funnnel led down to a curved pipe which arched back over the funnel. The weight of the water was supposed to be unbalanced, so the water would constantly fall from the arched pipe opening into the funnel, and so on.
The explanation given was that it was a fallacy for there to be an inbalance, by the principles of hydraulics. In truth, water would simply reach its own level in any container, or system of connected containers. I had just read, though, of capillary action. I thought that a capillary tube could create the needed balance if added to the original scheme.
I was so sure that I sent off a diagram to the current President, John F. Kennedy. I actual expected a hefty check in return for the idea. For some reason, JFK was busy elsewhere, and some flunky handled my correspondence. He gently encouraged me to continue with my interest and study of science.