Passage 8.11.1
μετὰ δὲ τὸ ἱερὸν τοῦ Ποσειδῶνος χωρίον ὑποδέξεταί σε δρυῶν πλῆρες, καλούμενον Πέλαγος, καὶ ἐκ Μαντινείας ἡ ἐς Τεγέαν ὁδὸς φέρει διὰ τῶν δρυῶν. Μαντινεῦσι δὲ ὅροι πρὸς Τεγεάτας εἰσὶν ὁ περιφερὴς ἐν τῇ λεωφόρῳ βωμός. εἰ δὲ ἀπὸ τοῦ ἱεροῦ τοῦ Ποσειδῶνος ἐς ἀριστερὰν ἐκτραπῆναι θελήσειας, σταδίους τε ἥξεις μάλιστά που πέντε καὶ ἐπὶ τῶν Πελίου θυγατέρων ἀφίξῃ τοὺς τάφους· ταύτας φασὶν οἱ Μαντινεῖς μετοικῆσαι παρὰ σφᾶς, τὰ ἐπὶ τῷ θανάτῳ τοῦ πατρὸς ὀνείδη φευγούσας.
After the sanctuary of Poseidon, you will come upon a place full of oak trees, called Pelagos ("Sea"), and the road from Mantineia to Tegea passes through these oaks. On the boundaries between Mantineia and Tegea there is a round altar by the roadside. If, however, you wish to turn left from Poseidon's sanctuary, you will go about five stades and arrive at the tombs of the daughters of Pelias. The Mantineans say these women settled among them when fleeing from the reproaches connected to the death of their father.