Passage 3.20.8
τὴν δὲ ἐπʼ Ἀρκαδίας ἰοῦσιν ἐκ Σπάρτης Ἀθηνᾶς ἕστηκεν ἐπίκλησιν Παρείας ἄγαλμα ἐν ὑπαίθρῳ, μετὰ δὲ αὐτὸ ἱερόν ἐστιν Ἀχιλλέως· ἀνοίγειν δὲ αὐτὸ οὐ νομίζουσιν· ὁπόσοι δʼ ἂν τῶν ἐφήβων ἀγωνιεῖσθαι μέλλωσιν ἐν τῷ Πλατανιστᾷ, καθέστηκεν αὐτοῖς τῷ Ἀχιλλεῖ πρὸ τῆς μάχης θύειν. ποιῆσαι δέ σφισι τὸ ἱερὸν Σπαρτιᾶται λέγουσι Πράκα ἀπόγονον τρίτον Περγάμου τοῦ Νεοπτολέμου.
On the road from Sparta toward Arcadia stands a statue of Athena called "Pareia" in the open air; beyond it is a sanctuary of Achilles. It is not customary for them to open it, but all those youths intending to compete in the games at Platanistas are required to sacrifice to Achilles before their contest. The Spartans say that this sanctuary was built for them by Prax, a descendant in the third generation from Pergamos, the son of Neoptolemus.