Let it be your constant method to look into the design of people's actions, and see what they would be at, as often as it is practicable; and to make this custom the more significant, practice it first upon yourself.
Source: Meditations, bk. 10, sct. 37.
-- Marcus Aurelius Antoninus, (Apr 20 121-180), Roman ruler, philosopher, author; He was Roman emperor, 161-180 and advocated stoicism in his Meditations.