Divinity Atlas
Ptolemy's bounds divide every sign's thirty degrees among five planets, Jupiter, Venus, Mercury, Mars and Saturn, in five unequal spans handed down from Egyptian astrology. A reading finds the term a sun's exact degree falls under and reads that planet's rulership over it, at the term's true classical width rather than an equal slice of the sign.
History
Dividing each sign among five planetary rulers in unequal spans is documented in Hellenistic astrology, and its most influential surviving codification is Ptolemy's Tetrabiblos, the second century CE text that has already shaped several of this atlas's other astrological report items. Ptolemy himself records that more than one such system circulated in his own time, a Chaldean division and a standard Greek assignment among them, and explicitly attributes the specific unequal-width version this report item uses to an earlier Egyptian source, which is why it is commonly called the Egyptian terms, or simply Ptolemy's terms, in modern astrological writing. This particular version remained the most widely used bounds system through the medieval and Renaissance periods, appearing in essential dignity calculations across that whole span.
The Five Rulers
Every sign's thirty degrees is shared among the same five planets, in an order and at spans that differ sign by sign: Jupiter, Venus, Mercury, Mars and Saturn are the five rulers the terms are divided among, never the Sun or Moon, and never in equal shares.
How A Reading Is Constructed
A reading finds the exact degree of the sun, or another chosen chart point, within its sign, then names the one of the five terms that degree falls under at its true classical width, unequal from one term to the next, and reads that ruling planet's dignity as a further layer over the sign itself, following Ptolemy's own Egyptian-attributed division rather than dividing the sign into five equal six degree slices.