I have made as many as eighteen [rather definitive sketches of cattle] in one month..
Notes from Wikiquote
A friend of Troyon relates how the painter, after his return in 1855 from a sketching tour in Touraine, showed him what seemed an almost endless panorama of great, splendid studies of cattle, most of which were, indeed, finished pictures; and when he expressed astonishment at their number and beauty, Troyon responded quietly