Plato, Letters 360b

τῷ παρακατακειμένῳ—ἦν δʼ οὗτος τῶν καλῶν τις—ὃς τότε εἶπεν· ἦ που πολλά, ὦ Διονύσιε, εἰς σοφίαν ὠφελῇ ὑπὸ Πλάτωνος· σὺ δʼ εἶπες· καὶ εἰς ἄλλα πολλά, ἐπεὶ καὶ ἀπʼ αὐτῆς τῆς μεταπέμψεως, ὅτι μετεπεμψάμην αὐτόν, διʼ αὐτὸ τοῦτο εὐθὺς ὠφελήθην. τοῦτʼ οὖν διασωστέον, ὅπως ἂν αὐξάνηται ἀεὶ ἡμῶν ἡ ἀπʼ ἀλλήλων ὠφελία. καὶ ἐγὼ νῦν τοῦτʼ αὐτὸ παρασκευάζων, τῶν τε Πυθαγορείων πέμπω σοι καὶ τῶν διαιρέσεων, καὶ ἄνδρα, ὥσπερ ἐδόκει ἡμῖν τότε,

which I thought excellent, as also did my neighbor at the table, who was one of the beautiful youths. And he then said—No doubt, Dionysius, you find Plato of great benefit as regards philosophy! And you replied—Yes, and in regard to much else; since from the very moment of my inviting him I derived benefit at once from the very fact that I had invited him. This tone, then, should be carefully preserved, in order that the mutual benefit we derive from one another may always go on increasing. So by way of helping towards this end I am now sending you some of the Pythagorean works and of the Divisions, and also, as we arranged at that time, a man of whom