Happy Birthday, Leonardo!

from Writer's Almanac (American Public Media, Garrison Keillor):
April 15 is the birthday of Leonardo da Vinci, born Lionardo di ser Piero da Vinci, in Vinci, Italy (1452). He's best known for his Mona Lisa and The Last Supper, two of the most famous paintings in the world, but he left fewer than 30 paintings when he died, and most of those were unfinished. He was a perfectionist and procrastinator, having worked on the Mona Lisa on and off for the last 15 years of his life. The Last Supper was likely only finished because his patron threatened to cut off his money. He spent much of his time drawing up plans for inventions like the submarine, the helicopter, the armored tank, and even the alarm clock, none of which came to fruition in his lifetime. Remaining today are at least 6,000 pages of his drawings and notes on everything from astronomy to anatomy — mostly written backward, decipherable only in a mirror. When he died, he apologized "to God and Man for leaving so much undone."