From David Litwa's, Lesous Deus:
LIGHT
I noted above that brilliant light imagery is perhaps the most common sign of an epiphany in the ancient Mediterranean world. In a childhood epiphany of Heracles’s divinity, for example, the house is flooded with light, and his parents “can see the walls as clearly as if it was bright dawn” (Theocr., Idylls 24.22, 38). In a dream epiphany to Aeneas, the divine Penates are “manifest in brilliant light” (multo manifesti lumine) (Virg., Aen. 3.151). Aeneas later tells Dido that he saw Mercury come to him manifesto in lumine (“in clear light”) (4.358). Venus later appears to Aeneas “bright white amidst ethereal clouds” (aetherios inter . . . candida nimbos) (8.608).73 The fact that Moses’ splendor is “sun-like” in Philo (Mos. 2.70) also recalls texts in which the Jewish deity has “the appearance of the sun” (1 En. 14:20; cf. Rev. 1:16).74
In the ancient world, some of the gods who shone so brightly were also human kings. On gold coins, Ptolemy III Euergetes (246–221 bce), Ptolemy V Epiphanes (204–180 bce), and Ptolemy VIII (144–116 bce) are all depicted with sun-like crowns beaming with light. The Seleucid kings Antiochus IV Epiphanes (175–164 bce), Antiochus VI Epiphanes Dionysus (145–42 bce) and Tryphon Diodotus (142–139 bce) portrayed themselves on coins with a nimbus of radiating light.75 This corona radiata in the royal context “is clearly meant to indicate apotheosis.”76 For an ancient Mediterranean reader, a kingly Moses could also appear in a divine light.
LIGHT
Finally—and most importantly—Mark uses light as a signal for Jesus’ divine status, and specifically the light of his clothing. Jesus’ garments, to quote the text, become “dazzling, extremely white” (στίλβοντα λευκὰ λίαν) (Mark 9:3). When introducing this chapter, I provided several examples of divine beings wearing garments of light. Additional instances are not difficult to find. The “splendid fine-woven garment” of the god Helios, “shimmers about him” (Hom. Hymn Sol. 31.13). Selene, the goddess of the Moon, has “garments that gleam from afar (εἵματα ... τηλαυγέα)” (Hom. Hymn Lun. 32.8). Yahweh is “wrapped in light as with a cloak” (ἀναβαλλόμενος φῶς ὡς ἱμάτιον) (Ps. 103:2 LXX).95