A Treatise on Painting is a collection of Leonardo da Vinci's writings entered in his notebooks under the general heading "On Painting". The manuscripts were gathered together by Francesco Melzi some time before 1542 and first printed in French and Italian as Trattato della pittura by Raffaelo du Fresne in 1651. The main aim of the treatise was to argue that painting was a science. Leonardo's keen observation of expression and character is evidenced in his comparison of laughing and weeping, about which he notes that the only difference between the two emotions in terms of the "motion of the [facial] features" is "the ruffling of the brows, which is added in weeping, but more elevated and extended in laughing."
