evidence: This is most probably a made up quote. Checking later editions was unfruitful, but Leonardo is so long out of these filthy copyright laws, we might as well look at J.P. Richter: "Leonardo. The Complete Works", 1888; found on Wikipedia: The Notebooks of Leonardo Da Vinci. What is in there that has some semblance to the desired quote? [...] As this is a "really nice" quote and all over the net, we have to look for an exact quote with sources. Those are always absent. Rule of thumb: if a quote on the net doesn't give the exact location to look it up for yourself, it is a lie.