Ammianus Marcellinus
 

XIV 6,17.
... finally the throng of eunuchs, beginning with the old men and ending with the boys, sallow and disfigured by the distorted form of their members; so that, wherever anyone goes, beholding the troops of mutilated men, he would curse the memory of that Queen Semiramis of old, who was the first of all to castrate young males, thus doing violence, as it were, to nature and wresting her from her intended course, since at the very beginning of life, through the primitive founts of the seed, by a kind of secret law, shows the ways to propagate posterity.

XVI 7,4-9.
The subject prompts me to add a few facts about this same Eutherius, perhaps hardly to be credited, for the reason that if a Numa Pompilius or a Socrates should give any good report of a eunuch and should back their statements by a solemn oath, they would be charged with having departed from the truth. But among brambles roses spring up, and among savage beasts some are tamed. Accordingly, I shall give a brief summary of the chief facts known about him.
He was born in Armenia of free parents, but when still very young he was kidnapped by hostile tribesmen in that neighborhood, who gelded him and sold him to some Roman traders and brought to Constantine's palace. There, as he grew up, he gradually gave evidence of virtuous living and ambition. He received as much training in letters as might suffice for one of that station; conspicuous for his remarkable keenness in devising and finding out difficult and knotty problems, he had extraordinary powers of memory; he was eager to do kindnesses and full of good counsel. And if the emperor Constans had listened to him in times past, when Eutherius had grown up and was already mature, and urged honourable and upright conduct upon him, he would have been guilty of no faults, or at least of only pardonable ones.
When he had become head chamberlain, he would sometimes criticize even Julian, as trained in the manners of Asia and therefore inconstant. Finally going into retirement, but afterwards summoned to the palace, always temperate and especially consistent, he so cultivated the noble virtues of loyalty and self-restraint that he was never charged, as the rest have been, with having disclosed a secret, unless it were to save another's life, or to have been kindled with a desire to increase his wealth.
The result was, that when he presently retired to Rome and grew old there in a permanent home, he carried about with him a good conscience as his companion; he was honored and loved by all classes, whereas that type of man [id genus homines], after amassing wealth by iniquitous means, usually seeks out secret lurking-places, like creatures of darkness shunning the sight of the multitude they have wronged.
In unrolling many records of the past, to see to which of the eunuchs of old I ought to compare him, I could find none. True, there were in times gone by those that were loyal and virtuous (although very few), but they were stained with some vice or other. For along with the excellent qualities which any one of them had acquired by studious endeavor or natural ability he was either extortionate or despicable for his cruelty, or too prone to do mischief, or too subservient to the rulers, or insolent through pride of power; but of one so well equipped in every direction I confess I have neither read nor heard, although I have relied on the abundant testimony of our age.
But if haply any curious student of ancient history should confront me with Menophilus, the eunuch of Mithridates, king of Pontus, let this reminder recall to him that nothing was recorded of Menophilus save this one fact, that in the supreme crisis he made a glorious showing.

XVIII 4,2-5.
And when news of this [attack by the Persian king] came, at first by rumours and then by trustworthy messengers, and great dread of impending disasters held all in suspense, the forge of the courtiers, hammering day and night at the instigation of the eunuchs on the same anvil (as the saying is), held up Ursicinus to the suspicious and timid emperor as a grim-visaged gorgon, often reiterating these and similar charges: that he, having on the death of Silvanus been sent as if in default of better men, to defend the east, was panting for higher honours.
Furthermore, by this foul and excessive flattery very many strove to purchase the favour of Eusebius, then head-chamberlain, upon whom (if the truth must be told) Constantius greatly depended, and who was vigorously attacking the safety of the aforesaid commander of the cavalry for a double reason: because he alone of all was not, like the rest, adding to Eusebius' wealth, and would not give up to him his house at Antioch, which the head chamberlain most importunately demanded.
Eusebius then, like a viper swelling with abundant poison and arousing its multitudinous brood to mischief when they were still barely able to crawl, sent out his chamberlains, already well grown, with directions that, amid the duties of their more private attendance, with the soft utterances of voices always childish and persuasive they should with bitter hatred batter the reputation of that brave man in the too receptive ears of the prince. And they promptly did what they were ordered.
Through disgust with these and their kind, I take pleasure in praising Domitian of old, for although, unlike his father and his brother, he drenched the memory of his name with indelible detestation, yet he won distinction by a most highly approved law, by which he had under heavy penalties forbidden anyone within the bounds of the Roman jurisdiction to geld a boy; for if this had not happened, who could endure the swarms of those whose small number is with difficulty tolerated?