On Mount Etna the words freeze in your mouth and you may make ice of them.[Footnote 2: There is no clue to explain this strange sentence.]
Just as iron rusts unless it is used, and water putrifies or, in cold, turns to ice, so our intellect spoils unless it is kept in use.
You do ill if you praise, and still worse if you reprove in a matter you do not understand.
When Fortune comes, seize her in front with a sure hand, because behind she is bald.
Taken from The Notebooks of Leonardo da Vinci edited by Jean Paul Richter, 1880.