There is a famous story of an experienced astronomer setting his beard on fire because he left the cap off his telescopes finder. I know it's said to be true of Galileo, but I thing it's relatively recent - i.e. 20th century. Does anyone know his name? Or can someone cite a source?
From the book Turn Left at Orion by Guy Consolmagno and Dan M. Davis, Galileo might have set his beard on fire with a telescope pointed at the Sun.
And you must keep your eyes -- and your clothing -- out of the path of the projected light. It is said that Galileo set fire to his beard doing this!
In his defense, he was the first person to look at the Sun with a telescope, so you can't blame him for not knowing about the associated risks!
But this story might also be apocryphal. Many people set various things on fire with a telescope (some even doing it on purpose).