Not sure which is the earlier memory, but one-burning myself on a soldering iron tip at my old man's old workshop. Can't remember what I was using it to build at the time though.
And teaching myself to go mushroom picking, using the various field guides I had, and some more advanced textbooks on mycology. Was around 3-4 in both cases. Might just go later actually, as the fly agarics, and peppery boletes are out, and its high time I went picking again.