Kautilya: Arthashastra(ca. 400 BCE–300 CE)
Book 1: Concerning Discipline
Chapter XIX: The Duties of a King
If a king is energetic, his subjects will be equally energetic. If he is reckless, they will not only be reckless likewise, but also eat into his works. Besides, a reckless king will easily fall into the hands of his enemies. Hence the king shall ever be wakeful.
He shall divide both the day and the night into eight nálikas (1½ hours), or according to the length of the shadow (cast by a gnomon standing in the sun): the shadow of three purushás (36 angulás or inches), of one purushá (12 inches), of four...
Source: R. Shamasastry, trans. Arthashastra. Bangalore: Government Press, 1915.