Passage 8.12.4
καί πως ὁ Ἡρακλῆς ἐρχόμενος τὴν ὁδὸν ταύτην ἐπήκουσε τῆς κίσσης καὶ---ἐνόμισε γὰρ παιδὸς εἶναι καὶ οὐκ ὄρνιθος τὸν κλαυθμόν---ἐτράπετο εὐθὺ τῆς φωνῆς· γνωρίσας δὲ αὐτήν τε ἔλυσεν ἀπὸ τῶν δεσμῶν καὶ τὸν παῖδα ἀνεσώσατο. ἐξ ἐκείνου δὲ ἡ πλησίον πηγὴ Κίσσα ἀπὸ τῆς ὄρνιθος ὀνομάζεται. τεσσαράκοντα δὲ ἀπὸ τῆς πηγῆς στάδια ἀφέστηκε Πετροσάκα καλούμενον χωρίον· Μεγαλοπολιτῶν δὲ καὶ Μαντινέων ὅρος ἐστὶν ἡ Πετροσάκα.
Once, when Heracles was traveling along this road, he heard the sound of the kissa (jay)—for he believed that the wailing belonged to a child rather than a bird—and promptly turned in the direction of the cry. Recognizing the bird, he freed it from its bonds and rescued the child. From that time forward, the nearby spring was named "Kissa" after the bird. A place called Petrosaka lies forty stades distant from the spring; Petrosaka serves as a boundary between Megalopolis and Mantineia.