The Babylonians may have been the first to set out the concept of house division. Specifically, they timed the birth according to three systems of time division: (a) a three-part division of the night into watches, (b) a four-part division of the nychthemeron with respect to sunrise and sunset, and (c) a twelve-part division of the day-time into hours. Babylonian astronomers studied the rising times of the signs and calculated tables of ascensions for their latitude, but it would take better time measurements by the Egyptians and the introduction of the concept of ascendant, around the 2nd century B.C., to give astrological houses their first recognisable structure and meaning, from the perspective of Classical Western astrology.