Aquarius is the eleventh sign, fixed, airy and ruled in the classical scheme by Saturn, which holds it as its day house alongside Capricorn as its night house; modern astrology has since assigned it to Uranus, discovered in 1781, and that reassignment is a little over two centuries old and should be dated rather than treated as traditional. No planet is exalted in Aquarius. The sign falls in the depth of winter, and the classical reading is of fixed air: a settled and impersonal quality, form held apart from matter. The eleventh house of the natural chart, which corresponds to it, carries friends, allies, groups and hopes, and the sign's association with collectives and with the general rather than the particular comes as much from that house correspondence as from anything in the figure.
Aquarius's three decans run Venus, Mercury, Moon, continuing the sequence from Capricorn's final Sun decan. As an air sign, Aquarius's triplicity is Saturn by day and Mercury by night, agreeing exactly across the Ptolemaic and Dorothean tables with Gemini and Libra; the air triplicity is unanimous among the classical sources, and the genuine dispute recorded under Cancer, Scorpio and Pisces does not touch it. The reassignment of Aquarius's rulership to Uranus is also a clear illustration of how a modern planet's supposed nature was worked out after the fact: Uranus was named for the Greek sky-god only in the late eighteenth century, some years after its discovery, and its character as a disruptive, revolutionary planet was constructed by nineteenth and twentieth century astrologers explicitly to suit an air sign already tied to the unconventional, rather than derived independently and found to fit.