Astronomicon, Book I

270-432 From these classifications of the signs according to their natures and qualities we pass to their configurations or aspects, that is their conjunction by certain geometrical lines or figures. The most obvious and striking of these local relations, direct opposition, is postponed till verse 395: the trine and square and sextile aspects are given precedence, and first among them comes the prime favorite of astrologers, the trigon.

Firm. II 22 1 (quoted in my note), Paul. Alex. E, Ptol. tetr. p. 9u., Porph. isag. p. 186, Gemin. isag. 2, Sext. emp. against the astronomers 39, Hermipp. I 19. Some of these authors ignore the hexagon, some the direct opposition, some both; Geminus adds syzygia [conjunction], to which Manilius will come at verse 466.

273-286 In the circle of the zodiac there are inscribed four equilateral triangles, in such manner that each angle falls upon a different sign: the signs are thus grouped in the following trigons.

1. Aries Leo Sagittarius.
2. Taurus Virgo Capricornus.
3. Gemini Libra Aquarius.
4. Cancer Scorpius Pisces.

A circular diagram of the zodiac signs. Inscribed within the circle are four overlapping equilateral triangles, forming a twelve-pointed star configuration. The vertices of the triangles point to the various zodiac symbols arranged around the outer edge. The triangles are labeled with the numbers 1, 2, 3, and 4 near their respective points. Below the circle, the word "TRIGONA" is centered.

Gemin. 2 7 (quoted in my note on verse 282), Ptol. tetr. pp. 10u.-11, Paul. Alex. B, Firm. II 22 3, 23 4.