Passage 3.8.1
Ἀρχιδάμου δὲ ὡς ἐτελεύτα καταλιπόντος παῖδας Ἆγίς τε πρεσβύτερος ἦν ἡλικίᾳ καὶ παρέλαβεν ἀντὶ Ἀγησιλάου τὴν ἀρχήν. ἐγένετο δὲ Ἀρχιδάμῳ καὶ θυγάτηρ, ὄνομα μὲν Κυνίσκα, φιλοτιμότατα δὲ ἐς τὸν ἀγῶνα ἔσχε τὸν Ὀλυμπικόν καὶ πρώτη τε ἱπποτρόφησε γυναικῶν καὶ νίκην ἀνείλετο Ὀλυμπικὴν πρώτη. Κυνίσκας δὲ ὕστερον γυναιξὶ καὶ ἄλλαις καὶ μάλιστα ταῖς ἐκ Λακεδαίμονος γεγόνασιν Ὀλυμπικαὶ νῖκαι, ὧν ἡ ἐπιφανεστέρα ἐς τὰς νίκας οὐδεμία ἐστὶν αὐτῆς.
When Archidamus died, he left behind sons, of whom Agis was the elder in age, and succeeded Agesilaus in the kingship. Archidamus also had a daughter named Cynisca, who was exceedingly ambitious in regard to the Olympic games and became the first woman to breed horses and also the first woman to achieve an Olympic victory. After Cynisca other women gained Olympic victories, especially those from Sparta, but none equaled her in fame for their successes.