Passage 6.23.1
ἐν δὲ Ἤλιδι τὰ ἄξια μνήμης γυμνάσιόν ἐστιν ἀρχαῖον· καὶ ὅσα ἐς τοὺς ἀθλητὰς πρὶν ἢ ἐς Ὀλυμπίαν ἀφικνεῖσθαι νομίζουσιν, ἐν τούτῳ σφίσι τῷ γυμνασίῳ δρᾶν καθέστηκε. πλάτανοι μὲν ὑψηλαὶ διὰ τῶν δρόμων πεφύκασιν ἐντὸς τοίχου· ὁ σύμπας δὲ οὗτος περίβολος καλεῖται Ξυστός, ὅτι Ἡρακλεῖ τῷ Ἀμφιτρύωνος ἐς ἄσκησιν ἐγίνετο, ὅσαι τῶν ἀκανθῶν ἐφύοντο ἐνταῦθα ἐπὶ ἑκάστῃ ἡμέρᾳ σφᾶς ἀναξύειν.
In Elis, among the noteworthy sights is an ancient gymnasium. All the customary rites for athletes before they proceed to Olympia are performed by them here in this gymnasium. Tall plane trees grow along the running-tracks within the enclosure walls. The entire enclosure is called Xystos, because Heracles, the son of Amphitryon, practiced here, daily scraping away the thistles (xysta) that grew in the place.