Here are some selected quotes from Leonardo Da Vinci's writings:
Philosophy
"Supreme happiness will be the greatest cause of misery, and the perfection of wisdom the occaison of folly."
"Every part is disposed to untie with the whole, that it may thereby escape from its own incompleteness."
"The soul derives to dwell with the body because without the members of that body it can neither act nor feel."
"O Time, thou that counsumest all things! O envious age, whereby all things are consumed!"
"The age as it flies glides secretly and deceives one and another; nothing
is more fleeting than the years, but he who sows virtue reaps honour."
"The air as soon as their is light is filled with innumerable images to which the eye serves as a magnet."
"There is no result in nature without a cause; understand the cause and you will have no need of experiment."
"The body of the earth is the nature of a fish, a grampus or sperm whale,
because it draws water as its breath instead of air."
"While I thought that I was learnign how to live, I have been learnign how to die"
"He who expects from experience what she does not posess takes leave of that reason"
"Intellectual passion drives out sesuality"
- (taken from Codice Atlantico, by Leonardo Da Vinci. translated.)