Lactantius Placidus was a grammarian who seems to have lived in the fifth century AD. Here he comments on a passage from the Thebaid I. 717 ff by Statius, a Roman poet who lived in the second half of the first century AD.
Whether it please thee to hear the name of ruddy Titan after the manner of the Achaemenian race, or Osiris lord of the crops, or Mithra as beneath rocks of the Persian cave he presses back the horns that resist his control.
a) He [Statius] declares that different nations give to Apollo different names. The Achaemenians call him Titan, the Egyptian Osiris, the Persians Mithra and worship him in a cave. The expression "resist his control" has reference to the figure of Mithra holding back the horns of a recalcitrant bull, whereby is indicated the Sun's illumination of the Moon, when the latter receives its rays.
b) The Egyptians regard Osiris as the Sun, by whom they think success may be assured to the crops... These rites were first observed by the Persians, from whom the Phrygians received them, and from the Phrygians the Romans. The Persians give to the Sun the native name of Mithra, as Hostanes [Ostanes] relates.
c) The Persians are known as Achaemenians from Achaemenes, son of Perseus and Andromeda, who ruled there. They call the Sun Apollo, and are said to have initiated the rites in his honour.
d) The Persians are said to have been the first to worship the Sun in caverns. For he is represented in a cavern in Persian dress with a turban, grasping the horns of a bull with both hands. The figure is interpreted of the Moon; for reluctant to follow his brother he meets him full and his light is obscured. In these verses the mysteries of the rites of the Sun are set forth. For in proof that the Moon is inferior and of less power the Sun is seated on the bull and grasps its horns. By which words Statius intended the two-horned moon to be understood, not the animal on which he rides.
e) The meaning is as follows: The Persians worship the Sun in caverns, and this Sun is in their own language known as Mithra, who as suffering eclipse is worshipped within a cave. The Sun himself moreover is represented with the face of a lion with turban and in Persian dress, with both hands grasping the horns of an ox. And this figure is interpreted of the Moon, which reluctant to follow its brother meets him full and obscures his light. He has revealed further a part of the mysteries. The Sun therefore presses down the bull as though to show that the Moon is inferior. He has laid especial stress moreover on the horns, in order that attention may be more clearly called to the Moon, and not to the animal on which she is represented as riding. Since however this is not the place to discuss the mysteries of those gods on the lines of an abstract philosophy, I will add a few words with regard to the symbols employed. The Sun is supreme, and because he treads down and controls the chief constellation, that is to say the Lion, he is himself represented with this face; or the reason may be that he surpasses the rest of the gods in power and energy, as the lion other wild beasts, or because of its impetuosity. The Moon however being nearer to the bull controls and leads it, and is represented as a cow. But these gods of divine and royal estate as they appear in the world are without mortal form either of a man or beast, having neither beginning nor end nor an intermediate part as other and lesser deities, as he himself declares above: "next comes the crowd of the wandering demigods." For that is necessitated by the attribute of eternity.
f) He gives to the rocks of a Persian cavern the name of temple of Perseus in virtue of the representation there of Phoebus as drawing to himself the Moon the latter goes in advance of the Sun, and in so doing gradually loses her own light, until she ceases entirely to shine. Approaching the Sun however at length she renews her light, and then follows the Sun. Moreover at the full, being now nearest to the Sun, she is said to be grasped by him.