What He Tried to Prove:
That he was both an awesome inventor and that the law of gravity simply did not apply to him.
Franz Reichelt, a tailor by trade, dreamed of inventing a fashion accessory that would allow a person to float safely to the ground after falling from a great height (perhaps after jumping out of one of those new-fangled flying machines they were experimenting with at the time).
What He Actually Proved:
Newton's law of universal gravitation.
More specifically, he proved that falling from a great height will result in death even if you happen to be wearing one of these convenient, comfy garments:
"Ladies, gentlemen... behold! My entire wardrobe, sewn together!"
Reichelt's "coat parachute," pictured above, was supposed to function in the same way as a modern parachute. The ultimate test of his invention was when, in 1912, he jumped off the Eiffel Tower in front of an assembled group of worried onlookers. You can pretty much imagine how that went.
Fortunately for the internet, but unfortunately for Reichelt, his tragic failure and subsequent impact with France was captured on what has to be one of the first ever examples of a viral video.