Dio Chrysostom, Discourses
36.34 (tr. J.W. Cohoon and H. Lamar Crosby):
So, as I was saying, it is reasonable to suppose that not only do those who busy themselves near some ritual, hard by the entrance to the sanctuary, gain some inkling of what is going on within, when either a lone mystic phrase rings out loudly, or fire appears above the enclosure, but also that there comes sometimes to the poets—I mean the very ancient poets—some utterance from the Muses, however brief, some inspiration of divine nature and of divine truth, like a flash of fire from the invisible.
οὐκοῦν, ὡς ἔφην, τούς τε πλησίον ἀναστρεφομένους τελετῆς τινος πρὸς ταῖς εἰσόδοις εἰκὸς τό γε τοσοῦτον τῶν ἔνδοθεν αἰσθάνεσθαί τινος, ἤτοι ῥήματος ἐκβοηθέντος ἑνὸς μυστικοῦ ἢ πυρὸς ὑπερφανέντος, καὶ τοῖς ποιηταῖς ἐνίοτε, λέγω δὲ τοῖς πάνυ ἀρχαίοις, φωνή τις ἐκ Μουσῶν ἀφίκετο βραχεῖα καί πού τις ἐπίπνοια θείας φύσεώς τε καὶ ἀληθείας, καθάπερ αὐγὴ πυρὸς ἐξ ἀφανοῦς λάμψαντος.