Is this what you are looking for? (I'm not sure what the citing means here, but maybe this will give you a start in the right direction)
“For you must understand that if only you have hit off such an untidy composition in accordance with the subject, it will give all the more satisfaction when it is later clothed in the perfection appropriate to all its parts. I have seen shapes in clouds and on patchy walls that have roused me to beautiful inventions of various things, and even though such shapes totally lack finish in any single part, they were not yet devoid of perfection in their gestures or other movements."
~ Leonardo da Vinci, Precetti