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xkcd #2929: Good and Bad Ideas
(imgs.xkcd.com)
Alt text:
While it seemed like a fun prank at the time, I realize my prank fire extinguishers full of leaded gasoline were a mistake.
They worked pretty well when I was in high school marching band. I didn't drive yet so I didn't need road vision, they darkened while out at practice and were clear elsewhen. Got an actual pair of prescription sunglasses in flight school though.