De Natura Animalium 3:41
Ἵππους μονόκερως γῆ Ἰνδικὴ τίκτει, φασί, καὶ ὄνους μονόκερως ἡ αὐτὴ τρέφει, καὶ γίνεταί γε ἐκ τῶν κεράτων τῶνδε ἐκπώματα. καὶ εἴ τις ἐς αὐτὰ ἐμβάλοι φάρμακον θανατηφόρον, ὁ πιών, οὐδὲν ἐπιβουλὴ λυπήσει αὐτόν: ἔοικε γὰρ ἀμυντήριον τοῦ κακοῦ τὸ κέρας καὶ τοῦ ἵππου καὶ τοῦ ὄνου εἶναι.
English translation (A. F. Scholfield, 1958)
India produces one-horned horses, they say, and the same country fosters one-horned asses. And from these horns they make drinking-vessels, and if anyone puts a deadly poison in them and a man drinks, the plot will do him no harm. For it seems that the horn both of the horse and of the ass is an antidote to the poison.
In this passage Aelian adds another species to the unicorn family: in addition to the one-horned ass there is also a one-horned horse.
De Natura Animalium 4:52
Ὄνους ἀγρίους οὐκ ἐλάττους ἵππων τὰ μεγέθη ἐν Ἰνδοῖς γίνεσθαι πέπυσμαι. καὶ λευκοὺς μὲν τὸ ἄλλο εἶναι σῶμα, τήν γε μὴν κεφαλὴν ἔχειν πορφύρᾳ παραπλησίαν, τοὺς δὲ ὀφθαλμοὺς ἀποστέλλειν κυανοῦ χρόαν. κέρας δὲ ἔχειν ἐπὶ τῷ μετώπῳ ὅσον πήχεως τὸ μέγεθος καὶ ἡμίσεος προσέτι, καὶ τὸ μὲν κάτω μέρος τοῦ κέρατος εἶναι λευκόν, τὸ δὲ ἄνω φοινικοῦν, τό γε μὴν μέσον μέλαν δεινῶς. ἐκ δὴ τῶνδε τῶν ποικίλων κεράτων πίνειν Ἰνδοὺς ἀκούω, καὶ ταῦτα οὐ πάντας, ἀλλὰ τοὺς τῶν Ἰνδῶν κρατίστους, ἐκ διαστημάτων αὐτοῖς χρυσὸν περιχέαντας, οἱονεὶ ψελίοις τισὶ κοσμήσαντας βραχίονα ὡραῖον ἀγάλματος. καί φασι νόσων ἀφύκτων ἀμαθῆ καὶ ἄπειρον γίνεσθαι τὸν ἀπογευσάμενον ἐκ τοῦδε τοῦ κέρατος: μήτε γὰρ σπασμῷ ληφθῆναι ἂν αὐτὸν μήτε τῇ καλουμένῃ ἱερᾷ νόσῳ, μήτε μὴν διαφθαρῆναι φαρμάκοις. ἐὰν δέ τι καὶ πρότερον ᾖ πεπωκὼς κακόν, ἀνεμεῖν τοῦτο, καὶ ὑγιᾶ γίνεσθαι αὐτόν. πεπίστευται δὲ τοὺς ἄλλους τοὺς ἀνὰ πᾶσαν τὴν γῆν ὄνους καὶ ἡμέρους καὶ ἀγρίους καὶ τὰ ἄλλα μώνυχα θηρία ἀστραγάλους οὐκ ἔχειν, οὐδὲ μὴν ἐπὶ τῷ ἥπατι χολήν, ὄνους δὲ τοὺς Ἰνδοὺς λέγει Κτησίας τοὺς ἔχοντας τὸ κέρας ἀστραγάλους φορεῖν, καὶ ἀχόλους μὴ εἶναι: λέγονται δὲ οἱ ἀστράγαλοι μέλανες εἶναι, καὶ εἴ τις αὐτοὺς συντρίψειεν, εἶναι τοιοῦτοι καὶ τὰ ἔνδον. εἰσὶ δὲ καὶ ὤκιστοι οἵδε οὐ μόνον τῶν ὄνων, ἀλλὰ καὶ ἵππων καὶ ἐλάφων: καὶ ὑπάρχονται μὲν ἡσυχῆ τοῦ δρόμου, κατὰ μικρὰ δὲ ἐπιρρώννυνται, καὶ διώκειν ἐκείνους τοῦτο δὴ τὸ ποιητικὸν μεταθεῖν τὰ ἀκίχητά ἐστιν. ὅταν γε μὴν ὁ θῆλυς τέκῃ, καὶ περιάγηται τὰ ἀρτιγενῆ, σύννομοι αὐτοῖς οἱ πατέρες αὐτῶν φυλάττουσι τὰ βρέφη. διατριβαὶ δὲ τοῖς ὄνοις τῶν Ἰνδικῶν πεδίων τὰ ἐρημότατά ἐστιν. ἰόντων δὲ τῶν Ἰνδῶν ἐπὶ τὴν ἄγραν αὐτῶν, τὰ μὲν ἁπαλὰ καὶ ἔτι νεαρὰ ἑαυτῶν νέμεσθαι κατόπιν ἐῶσιν, αὐτοὶ δὲ ὑπερμαχοῦσι, καὶ ἴασι τοῖς ἱππεῦσιν ὁμόσε, καὶ τοῖς κέρασι παίουσι. τοσαύτη δὲ ἄρα ἡ ἰσχὺς ἡ τῶνδέ ἐστιν. οὐδὲν ἀντέχει αὐτοῖς παιόμενον, ἀλλὰ εἴκει καὶ διακόπτεται καὶ ἐὰν τύχῃ κατατέθλασται καὶ ἀχρεῖόν ἐστιν. ἤδη δὲ καὶ ἵππων πλευραῖς ἐμπεσόντες διέσχισαν καὶ τὰ σπλάγχνα ἐξέχεαν. ἔνθεν τοι καὶ ὀρρωδοῦσιν αὐτοῖς πλησιάζειν οἱ ἱππεῖς: τὸ γάρ τοι τίμημα τοῦ γενέσθαι πλησίον θάνατός ἐστιν οἴκτιστος αὐτοῖς, καὶ ἀπόλλυνται καὶ αὐτοὶ καὶ οἱ ἵπποι. δεινοὶ δέ εἰσι καὶ λακτίσαι. δήγματα δὲ ἄρα ἐς τοσοῦτον καθικνεῖται αὐτῶν, ὡς ἀποσπᾶν τὸ περιληφθὲν πᾶν. ζῶντα μὲν οὖν τέλειον οὐκ ἂν λάβοις, βάλλονται δὲ ἀκοντίοις καὶ οἰστοῖς, καὶ τὰ κέρατα ἐξ αὐτῶν Ἰνδοὶ νεκρῶν σκυλεύσαντες ὡς εἶπον περιέπουσιν. ὄνων δὲ Ἰνδῶν ἄβρωτόν ἐστι τὸ κρέας: τὸ δὲ αἴτιον, πέφυκεν εἶναι πικρότατον.
English translation (A. F. Scholfield, 1958)
I have learned that in India are born wild asses as big as horses. All their body is white except for the head, which approaches purple, while their eyes give off a dark blue colour. They have a horn on their forehead as much as a cubit and half long; the lower part of the horn is white, the upper part is crimson, while the middle is jet-black. From these variegated horns, I am told, the Indians drink, but not all, only the most eminent Indians, and round them at intervals they lay rings of gold, as though they were decorating a beautiful arm of a statue with bracelets. And they say that a man who has drunk from this horn knows not, and is free from, incurable diseases: he will never be seized with convulsions nor with the sacred sickness, as it is called, nor be destroyed by poisons. Moreover if he had previously drunk some deadly stuff, he vomits it up and is restored to health. It is believed that asses, both the tame and the wild kind, all the world over and all other beasts with uncloven hoofs are without knucklebones and without gall in the liver; whereas those horned asses of India, Ctesias says, have knucklebones and are not without gall. Their knucklebones are said to be black, and if ground down are black inside as well. And these animals are far swifter than any ass or even than any horse or any deer. They begin to run, it is true at a gentle pace, but gradually gather strength until to pursue them is, in the language of poetry, to chase the unattainable. When the dam gives birth and leads her new-born colts about, the sires herd with, and look after, them. And these Asses frequent the most desolate plains in India. So when the Indians go to hunt them, the Asses allow their colts, still tender and young, to pasture in their rear, while they themselves fight on their behalf and join battle with the horsemen and strike them with their horns. Now the strength of these horns is such that nothing can withstand their blows, but everything gives way and snaps or, it may be, is shattered and rendered useless. They have in the past even struck at the ribs of a horse, ripped it open, and disembowelled it. For that reason the horsemen dread coming to close quarters with them, since the penalty for so doing is a most lamentable death, and both they and their horses are killed. They can kick fearfully too. Moreover their bite goes so deep that they tear away everything that they have grasped. A full-grown ass one would never capture alive: they are shot with javelins and arrows, and when dead the Indians strip them of their horns, which, as I said, they decorate. But the flesh of Indian Asses is uneatable, the reason being that it is naturally exceedingly bitter.
De Natura Animalium 16:20
Ἐν τοῖς χωρίοις τοῖς ἐν Ἰνδίᾳ (λέγω δὲ τοῖς ἐνδοτάτω) ὄρη φασὶν εἶναι δύσβατά τε καὶ ἔνθηρα, καὶ ἔχειν ζῷα ὅσα καὶ ἡ καθ᾽ ἡμᾶς τρέφει γῆ, ἄγρια δέ: καὶ γάρ τοι καὶ τὰς οἶς τὰς ἐκεῖ φασιν εἶναι καὶ ταύτας θηρία, καὶ κύνας καὶ αἶγας καὶ βοῦς, αὐτόνομά τε ἀλᾶσθαι καὶ ἐλεύθερα, ἀφειμένα νομευτικῆς ἀρχῆς. πλήθη δὲ αὐτῶν καὶ ἀριθμοῦ πλείω φασὶν οἱ τῶν Ἰνδῶν λόγιοι. ἐν δὲ τοῖς καὶ τοὺς Βραχμᾶνας ἀριθμεῖν ἄξιον: καὶ γάρ τοι καὶ ἐκεῖνοι ὑπὲρ τῶνδε ὁμολογοῦσι τὰ αὐτά. λέγεται δὲ καὶ ζῷον ἐν τούτοις εἶναι μονόκερων, καὶ ὑπ᾽ αὐτῶν ὀνομάζεσθαι καρτάζωνον. καὶ μέγεθος μὲν ἔχειν ἵππου τοῦ τελείου καὶ λόφον, καὶ λάχνην ἔχειν ξανθήν, ποδῶν δὲ ἄριστα εἰληχέναι. καὶ τοὺς μὲν πόδας ἀδιαρθρώτους τε καὶ ἐμφερεῖς ἐλέφαντι πεφυκέναι, τὴν δὲ οὐρὰν ἔχειν συός: μέσον δὲ τῶν ὀφρύων ἔχειν ἐκπεφυκὸς κέρας οὐ λεῖον ἀλλὰ ἑλιγμοὺς ἔχον τινὰς καὶ μάλα αὐτοφυεῖς, καὶ εἶναι μέλαν τὴν χρόαν: λέγεται δὲ καὶ ὀξύτατον εἶναι τὸ κέρας ἐκεῖνο. φωνὴν δὲ ἔχειν τὸ θηρίον ἀκούω τοῦτο πάντων ἀπηχεστάτην τε καὶ γεγωνοτάτην. καὶ τῶν μὲν ἄλλων αὐτῷ ζῴων προσιόντων φέρειν καὶ πρᾶον εἶναι, λέγουσι δὲ ἄρα πρὸς τὸ ὁμόφυλον δύσεριν εἶναί πως. καὶ οὐ μόνον φασὶ τοῖς ἄρρεσιν εἶναί τινα συμφυῆ κύριξίν τε πρὸς ἀλλήλους καὶ μάχην, ἀλλὰ καὶ πρὸς τὰς θηλείας ἔχουσι θυμὸν τὸν αὐτόν, καὶ προάγοντες τὴν φιλονεικίαν καὶ μέχρι θανάτου τοῦ ἡττηθέντος ἐξάγουσιν. ἔστι μὲν οὖν καὶ διὰ παντὸς τοῦ σώματος ῥωμαλέον, ἀλκὴ δέ οἱ τοῦ κέρατος ἄμαχός ἐστι. νομὰς δὲ ἐρήμους ἀσπάζεται, καὶ πλανᾶται μόνον: ὥρᾳ δὲ ἀφροδίτης τῆς σφετέρας συνδυασθεὶς πρὸς τὴν θήλειαν πεπράυνται, καὶ μέντοι καὶ συννόμω ἐστόν. εἶτα ταύτης παραδραμούσης καὶ τῆς θηλείας κυούσης, ἐκθηριοῦται αὖθις, καὶ μονίας ἐστὶν ὅδε ὁ Ἰνδὸς καρτάζωνος. τούτων οὖν πώλους πάνυ νεαροὺς κομίζεσθαί φασι τῷ τῶν Πρασίων βασιλεῖ, καὶ τὴν ἀλκὴν ἐν ἀλλήλοις ἐπιδείκνυσθαι κατὰ τὰς θέας τὰς πανηγυρικάς. τέλειον δὲ ἁλῶναί ποτε οὐδεὶς μέμνηται.
English translation (A. F. Scholfield, 1958)
In certain regions of India (I mean in the very wild heart of the country) they say that there are impassable mountains full of wild life, and that they contain just as many animals as our own country produces, only wild. For they say that even the sheep there are wild, the dogs too and the goats and the cattle, and, that they roam at their own sweet will in freedom and uncontrolled by any herdsman. Indian historians assert that their numbers are past counting, and among the historians we must reckon the Brahmins, for they also agree in telling the same story.
And in these same regions there is said to exist a one-horned beast which they call Cartazonus. It is the size of a full-grown horse,' has the mane of a horse, reddish hair, and is very swift of foot. Its feet are, like those of the elephant, not articulated and it has the tail of a pig. Between its eyebrows it has a horn growing out; it is not smooth but has spirals of quite natural growth, and is black in colour. This horn is also, said to be exceedingly sharp. And I am told that the creature has the most discordant and powerful voice of all animals. When other animals approach, it does, not object but is gentle; with its own kind however it is inclined to be quarrelsome. And they say that not only do the males instinctively butt and fight one another, but that they display the same temper towards the females, and carry their contentiousness to such a length that it ends only in the death of their defeated rival. The fact is that strength resides in every part of the animals body, and the power of its horn is invincible. It likes lonely grazing-grounds where it roams in solitude, but at the mating season, when it associates with the female, it becomes gentle and the two even graze side by side. Later when the season has passed and the female is pregnant, the male Cartazonus of India reverts to its savage and solitary state. They say that the foals when quite young are taken to the King of the Prasii and exhibit their strength one against another in the public shows, but nobody remembers a full-grown animal having been captured.
Aelian's cartazon (καρτάζωνος) sounds very much like Pliny's monoceros, which, let us remind, has a head of a stag, feet of the elephant and a tail of a boar. We can suppose it is because Aelian drew from the same source as Pliny, likely Megasthenes'es Indica (not to confuse with the book written by Ctesias). The name probably comes from Persian "kargadan" and originates in Sanskrit khaḍgadhenu (खड्गधेनु), which means "female rhinoceros" (khadga खड्ग – rhinoceros, sword; dhenu धेनु – cow).
It must also be the Indian rhinoceros that supplied most of the description.
However, the rhinoceros's horn is curved and smooth, not straight and spiraled. That detail must have been borrowed from the Tibetan chiru, whose horns look exactly like the one described in text.
Aelian says that the cartazon has unarticulated legs, that is lacking joints. It was a popular misconception of Antiquity about elephants being unable to bend their legs. It was said that when an elephant wants to sleep, it leans onto a tree with its head and falls asleep standing.