Saturn rules Capricorn and Aquarius, is exalted in Libra, in detriment in Cancer and Leo and in fall in Aries. Ptolemy gives it a cold and dry nature, and it is the greater malefic and a planet of the diurnal sect. It is the outermost of the seven classical bodies and the slowest, taking about twenty-nine and a half years to complete the zodiac, which is the basis of the modern Saturn return, the point around ages twenty-nine, fifty-nine and eighty-eight when the planet comes back to its natal place; the term is twentieth-century though the underlying period is not. Its natural significations are time, limit, age, endurance, structure, land, bones, lead, cold, poverty, and everything slow, heavy, hidden or old. As the boundary of the visible solar system it was the traditional marker of the outermost sphere before the fixed stars.
The Latin name Saturn renders the Greek Kronos, who in turn renders the Babylonian planet-god Ninurta, a chain of translation reaching back through Babylonian celestial omen-reading of perhaps 1000 BCE to a Mesopotamian deity of agriculture and war whose character differs considerably from the stern, limiting Saturn later astrology describes. Ptolemy's Tetrabiblos, part of the Hellenistic synthesis of roughly the first century BCE to the second century CE, explains Saturn's cold, dry nature by its extreme distance, furthest of the seven classical bodies both from the Sun's heat and the moist exhalations of the earth, the same proximity-based reasoning the text applies throughout. As the outermost visible planet, Saturn also marked the traditional boundary of the observable cosmos before the fixed stars.