-Attributed to Leonardo da Vinci, Italian painter and inventor.

This quote is widely attributed to da Vinci himself, however no proof exists that he actually wrote or said it. The quote actually comes from a 1965 film about da Vinci, titled I, Leonardo da Vinci. The script was written by John H. Secondari, so it is most likely Secondari who actually wrote the words, but he was writing them for da Vinci to say, which creates a confusing bit of attribution. Still, da Vinci was fascinated with flight and spent great amounts of time pondering it, so the quote fits well into his headspace.