Fragments of the Philosophical Poets

But according to some, he wrote only two works: On the Solstice and On the Equinox, having judged other matters to be beyond understanding. It is thought, according to some, that he was the first to study astronomy and to predict solar eclipses and solstices, as Eudemus [fr. 94 Speng.] says in his History of Astronomy. For this reason, both Xenophanes [fr. 19] and Herodotus [I 74] admire him. Heraclitus [fr. 38] and Democritus also testify to this.

Some also say that he was the first to declare that souls are immortal; among these is the poet Choerilus [p. 182 Naeke]. He was also the first to discover the movement from solstice to solstice, and according to some, he was the first to state that the size of the sun ...and the size of the solar circle, just as that of the moon... is the seven-hundred-and-twentieth part of the solar circle. He was also the first to name the last day of the month the "thirtieth." He was the first to discourse on nature, as some say. Aristotle [De Anima A 2. 405a 19] and Hippias [fr. 10 FHG II 62] say that he even attributed soul to inanimate objects, inferring this from the magnet stone and amber. Pamphila [fr. 1, FHG III 520] says that having learned geometry from the Egyptians, he was the first to inscribe a right-angled triangle within a circle and sacrifice an ox. Others say Pythagoras did this, among whom is Apollodorus the Calculator [cf. Diog. VIII 12]. This passage regarding the discovery of scalene triangles and linear theory likely belongs to Pythagoras. He also appears to have been very wise in political affairs. For when Croesus sent to the Milesians to propose an alliance, Thales forbade it; this act saved the city when Cyrus conquered it. And he himself, as Heraclides [Ponticus fr. 47 Voss.] records, says that he remained a solitary and a private citizen.