Arnobius the Elder, Against the Pagans, book 5, 5-7 (here) has a long discussion of the cult of Cybele, the Great Mother, of which Attis is a part, and her castrated and infamous priests, the Galli:
5. In Timotheus, who was no mean mythologist, and also in others equally well informed, the birth of the Great Mother of the gods, and the origin of her rites, are thus detailed, being derived-as he himself writes and suggests-from learned books of antiquities, and from his acquaintance with the most secret mysteries:-
Within the confines of Phrygia, he says, there is a rock of unheard-of wildness in every respect, the name of which is Agdus, so named by the natives of that district. Stones taken from it, as Themis by her oracle had enjoined, Deucalion and Pyrrha threw upon the earth, at that time emptied of men; from which this Great Mother, too, as she is called, was fashioned along with the others, and animated by the deity. Her, given over to rest and sleep on the very summit of the rock, Jupiter assailed with lewdest desires. But when, after long strife, he could no accomplish what he had proposed to himself, he, baffled, spent his lust on the stone. This the rock received, and with many groanings Acdestis is born in the tenth month, being named from his mother rock.
In him there had been resistless might, and a fierceness of disposition beyond control, a lust made furious, and derived from both sexes. He violently plundered and laid waste; he scattered destruction wherever the ferocity of his disposition had led him; he regarded not gods nor men, nor did he think anything more powerful than himself; he contemned earth, heaven, and the stars.
6. Now, when it had been often considered in the councils of the gods, by what means it might be possible either to weaken or to curb his audacity, Liber, the rest hanging back, takes upon himself this task. With the strongest wine he drugs a spring much resorted to by Acdestis where he had been wont to assuage the heat and burning thirst roused in him by sport and hunting. Hither runs Acdestis to drink when he felt the need; he gulps down the draught too greedily into his gaping veins. Overcome by what he is quite unaccustomed to, he is in consequence sent fast asleep.
Liber is near the snare which he had set; over his foot he throws one end of a halter formed of hairs, woven together very skilfully; with the other end he lays hold of his privy members. When the fumes of the wine passed off, Acdestis starts up furiously, and his foot dragging the noose, by his own strength he robs himself of his sex; with the tearing asunder of these parts there is an immense flow of blood; both are carried off and swallowed up by the earth; from them there suddenly springs up, covered with fruit, a pomegranate tree, seeing the beauty of which, with admiration, Nana, daughter of the king or river Sangarius, gathers and places in her bosom some of the fruit.
By this she becomes pregnant; her father shuts her up, supposing that she had been debauched, and seeks to have her starved to death; she is kept alive by the mother of the gods with apples, and other food, and brings forth a child, but Sangarius orders it to be exposed.
One Phorbas having found the child, takes it home, brings it up on goats’ milk; and as handsome fellows are so named in Lydia, or because the Phrygians in their own way of speaking call their goats attagi, it happened in consequence that the boy obtained the name Attis.
Him the mother of the gods loved exceedingly, because he was of most surpassing beauty; and Acdestis, who was his companion, as he grew up fondling him, and bound to him by wicked compliance with his lust in the only way now possible, leading him through the wooded glades, and presenting him with the spoils of many wild beasts, which the boy Attis at first said boastfully were won by his own toil and labour. Afterwards, under the influence of wine, he admits that he is both loved by Acdestis, and honoured by him with the gifts brought from the forest; whence it is unlawful for those polluted by drinking wine to enter into his sanctuary, because it discovered his secret.
7. Then Midas, king of Pessinus, wishing to withdraw the youth from so disgraceful an intimacy, resolves to give him his own daughter in marriage, and caused the gates of the town to be closed, that no one of evil omen might disturb their marriage joys.
But the mother of the gods, knowing the fate of the youth, and that he would live among men in safety only so long as he was free from the ties of marriage, that no disaster might occur, enters the closed city, raising its walls with her head, which began to be crowned with towers in consequence. Acdestis, bursting with rage because of the boy’s being torn from himself, and brought to seek a wife, fills all the guests with frenzied madness: the Phrygians shriek aloud, panic-stricken at the appearance of the gods; a daughter of adulterous Gallus cuts off her breasts; Attis snatches the pipe borne by him who was goading them to frenzy; and he, too, now filled with furious passion, raving frantically and tossed about, throws himself down at last, and under a pine tree mutilates himself, saying, “Take these, Acdestis, for which you have stirred up so great and terribly perilous commotions.”
With the streaming blood his life flies; but the Great Mother of the gods gathers the parts which had been cut off, and throws earth on them, having first covered them, and wrapped them in the garment of the dead. From the blood which had flowed springs a flower, the violet, and with this the tree is girt. Thence the custom began and arose, whereby you even now veil and wreath with flowers the sacred pine.
The virgin who had been the bride, whose name, as Valerius the pontifex relates, was Ia, veils the breast of the lifeless youth with soft wool, sheds tears with Acdestis, and slays herself After her death her blood is changed into purple violets.
The mother of the gods sheds tears also, from which springs an almond tree, signifying the bitterness of death. Then she bears away to her cave the pine tree, beneath which Attis had unmanned himself; and Acdestis joining in her wailings, she beats and wounds her breast, pacing round the trunk of the tree now at rest.
Jupiter is begged by Acdestis that Attis may be restored to life: he does not permit it. What, however, fate allowed, he readily grants, that his body should not decay, that his hairs should always grow, that the least of his fingers should live, and should be kept ever in motion; content with which favours, it is said that Acdestis consecrated the body in Pessinus, and honoured it with yearly rites and priestly services.
And:
16. And yet how can you assert the falsehood of this story, when the very rites which you celebrate throughout the year testify that you believe these things to be true, and consider them perfectly trustworthy?
For what is the meaning of that pine which on fixed days you always bring into the sanctuary of the mother of the gods? Is it not in imitation of that tree, beneath which the raging and ill-fated youth laid hands upon himself, and which the parent of the gods consecrated to relieve her sorrow?
What mean the fleeces of wool with which you bind and surround the trunk of the tree? Is it not to recall the wools with which Ia covered the dying youth, and thought that she could procure some warmth for his limbs fast stiffening with cold? What mean the branches of the tree girt round and decked with wreaths of violets? Do they not mark this, how the Mother adorned with early flowers the pine which indicates and bears witness to the sad mishap?
What mean the Galli with dishevelled hair beating their breasts with their palms? Do they not recall to memory those lamentations with which the tower-bearing Mother, along with the weeping Acdestis, wailing aloud, followed the boy? What means the abstinence from eating bread which you have named castus? Is it not in imitation of the time when the goddess abstained from Ceres’ fruit in her vehement sorrow?
17. Or if the things which we say are not so declare, say yourselves-those effeminate and delicate men whom we see among you in the sacred rites of this deity-what business, what care, what concern have they there; and why do they like mourners wound their arms and breasts, and act as those dolefully circumstanced?
What mean the wreaths, what the violets, what the swathings, the coverings of soft wools? Why, finally, is the very pine, but a little before swaying to and fro among the shrubs, an utterly inert log, set up in the temple of the Mother of the gods next, like some propitious and very venerable deity?
For either this is the cause which we have found in your writings and treatises, and in that case it is clear that you do not celebrate divine rites, but give a representation of sad events; or if there is any other reason which the darkness of the mystery has withheld from us, even it also must be involved in the infamy of some shameful deed. For who would believe that there is any honour in that which the worthless Galli begin, effeminate debauchees complete?
And ch. 39:
39. Whence, then, do we prove that all these narratives are records of events? Froth the solemn rites and mysteries of initiation, it is clear, whether those which are celebrated at fixed times and on set days, or those which are taught secretly by the heathen without allowing the observance of their usages to be interrupted.
For it is not to be believed that these have no origin, are practised without reason or meaning, and have no causes connected with their first beginnings. That pine which is regularly born into the sanctuary of the Great Mother, is it not in imitation of that tree beneath which Attis mutilated and unmanned himself, which also, they relate, the goddess consecrated to relieve her grief? That erecting of phalli and fascina, which Greece worships and celebrates in rites every year, does it not recall the deed by which Liber paid his debt?