Also 8 tetrachty(s, 9 tetraktys. [a. Gr. τετρακτύς.] A set of four; the number four; esp. the Pythagorean name for the sum of the first four numbers (1 + 2 + 3 + 4 = 10) regarded as the source of all things.
1603. Holland, Plutarch’s Mor., 1317. That famous quaternarie of theirs, named Tetractys, which consisteth of foure nines, and amounteth to thirtie sixe, was their greatest oth.
1653. H. More, Conject. Cabbal., Pref. (1713), 4. The Pythagoreans Oath, swearing by him that taught them the mystery of the Tetractys, or the number Four.
a. 1774. Tucker, Lt. Nat. (1834), II. 415. Pythagoras had his tetrachty, his mystic numbers, his symbols.
1809. W. Irving, Knickerb., IV. iv. (1812), I. 236. From the Tetractys of Pythagoras, to the recondite works of Breshaw and mother Bunch.
1865. Grote, Plato, I. i. 12, note. The tetraktys (consecrated as the sum total of the first four numbers 1 + 2 + 3 + 4 = 10).
Hence Tetractysm, the Pythagorean doctrine of the tetractys.
1846. T. W. Jenkyn, Baxter’s Wks., Pref. 50. Those who understand … what Tetractysm was to the Pythagoreans will … comprehend what Triadism was to Baxter.
