Passage 2.38.7
ἀνατείνει δὲ ὑπὲρ τὰς κώμας ὄρος Πάρνων, καὶ Λακεδαιμονίων ἐπʼ αὐτοῦ πρὸς Ἀργείους ὅροι καὶ Τεγεάτας εἰσίν· ἑστήκασι δὲ ἐπὶ τοῖς ὅροις Ἑρμαῖ λίθου, καὶ τοῦ χωρίου τὸ ὄνομά ἐστιν ἀπʼ αὐτῶν. ποταμὸς δὲ καλούμενος Τάναος---εἷς γὰρ δὴ οὗτος ἐκ τοῦ Πάρνωνος κάτεισι---ῥέων διὰ τῆς Ἀργείας καὶ ἐκδίδωσιν ἐς τὸν Θυρεάτην κόλπον.
Mount Parnon rises above the villages, and upon it lie boundaries which separate the Lacedaemonians from both the Argives and the Tegeans. At these boundaries stand stone images of Hermes, from which the place takes its name. A river called Tanaus—the only one indeed that descends from Mount Parnon—flows through the Argive land and empties into the Thyreatic Gulf.