‘The term monoceros is originally of Greek origin, and comes from monos, meaning one, and keras, meaning a horn’.
Georg Caspar Kirchmaier, De basilisco, unicornu, phœnice, behemoth, leviathan, dracone, araneo, tarantula et ave paradisi, dissertationes aliquot (Wittenberg, 1669), p. 51. 
Image of a unicorn from Conrad Gessner, Historiae Animalium (Frankfurt, 1620), i, p. 689.
The unicorn is probably the most famous mythical creature of all. A favourite theme in literature and art, the legend of the unicorn has proved especially enduring. This illustration, from Worth’s copy of Gessner’s Historiae Animalium, like the famous early sixteenth-century tapestry of the Lady and the Unicorn, presents an idealised form of the animal: a single horned beast bearing a similarity to a horse. To this basic anatomical definition paganism and Christianity added more lore: a unicorn horn could be used to counteract poison, and it was said that the beast itself could only be tamed by a virgin. Christian scholars adopted the iconography linking the purity theme to Mary, the Mother of God, and, in addition, a hunt theme to the passion of Christ. This symbiosis ensured that the legend of the unicorn became a recognised topos throughout medieval and early modern art.
The legend of the unicorn predates this and is not solely a western European phenomenon: depictions of unicorns may also be found in Middle-Eastern and Asian iconography, and similarities have been drawn between the mythical unicorn and the ‘Qilin’ of the East. Equally, though western unicorns were usually depicted as white stallions with a long horn projecting from the middle of the forehead, not every author on the subject agreed with this archetypal depiction. Ancient writers, such as Ctesias and Pliny disagreed about the colour of a unicorn’s horn: for Ctesias, writing c. 400 BC, the horn ‘for about two palm-breadths upward from the base is of the purest white, where it tapers to a sharp point of a flaming crimson, and, in the middle, is black’. For Pliny (23-79 AD), writing in his Natural History, a unicorn possessed ‘a single black horn three feet long, projecting from the middle of the forehead’. That Pliny’s description proved influential may be seen in the almost verbatim use made of it by Joannes Jonstonus (1603-1675) in his Historiae naturalis de quadrupedibus libri (Amsterdam, 1657), a text likewise in the Worth Library: ‘As for the description of the Unicorne, he is said to resemble in his whole body the Horse: He is tailed like a Boor, grins and snarls like a Lyon, headed like an Hart, footed like an Elephant, furnish with one onely horn, and that a black one, two cubits long, standing in the midst of his fore-head’.
For early modern natural historians unicorns were very difficult to categorize since the literal early modern definition monoceros (an animal with one horn), inevitably included a whole range of different types. Gessner specifically draws attention to this in his discussion of unicorns, for he had already commented on other beasts with one horn, among them ‘Oxen in India’ and ‘the Bulls of Aonia’. The definition of a unicorn simply by the number of its horns thus led to confusion with actual one-horned animals, and it is likely that the legend of the ‘unicorn’ may well reflect encounters with animal such as the Indian rhinoceros or the Arabian oryx.
Image of a ‘Camphurch’ in Ulisse Aldrovandi, Monstrorum historia: cum paralipomenis historiæ omnium animalium. Bartholomæus Ambrosinus … labore, et studio volumen composuit; Marcus Antonius Bernia in lucem edidit (Bologna, 1642): Paralipomena, p. 113.
But, if the definition blurred the lines between real and mythical, it could also cause confusion between different types of mythical one-horned beasts. This image of a ‘camphurch’, from Worth’s copy of Aldrovandi’s Monstorum historia, presents yet another variant, an amphibious type of unicorn which was said to reside on the Island of Molucca. Though the length of its horn was superficially similar to a typical unicorn, there were distinct differences between the two – for where a unicorn had the hooves of a horse, a camphurch had webbed hind hooves. Ambroise Paré (c.1510-1590), in his book on monsters and marvels, gives the following description of a camphurch (one which is heavily reliant on that of the French explorer, André Threvet (1516-1590): ‘This animal is of the size of a hind, having one horn on the forehead, mobile, three and a half feet long, as thick as the arm of a man’.
Image of unicorns from Joannes Jonstonus, Historiae naturalis de quadrupedibus libri (Amsterdam, 1657), Tab. X .
Thus the use of ‘monoceros’ as a definition inevitably meant that the legendary and the mundane might easily be confused – and certainly there are a plethora of different types of ‘animals with one horn’ in the books in Edward Worth’s collection. The typology used by Georg Caspar Kirchmaier (1635-1700), in his treatise on the theory of unicorns, draws attention to this broader context in which unicorns were studied in early modern Germany. For Kirchmaier, a professor of rhetoric at the University of Wittenberg, the answer to this problem lay in philology. What was needed was an accurate definition, for in his view, ‘the majority of the false stories about the monoceros, which are not only monstrous but obscure, could not have arisen except through an indistinct apprehension of what the term signifies’. Joannes Jonstonus, in his Historiae naturalis de quadrupedibus libri (Amsterdam, 1657), agreed. He advocated a definition that properly only referred to one type of beast, the legendary unicorn of old:
‘The name of Monoceros, that among the Latines sounds so much, as a one-horned beast, agrees to many creatures; but in a strict sense, is retained to one alone – namely that, who from having but one horn, bears the name of Unicorn’.
Aldrovandi, Ulisse, Monstrorum historia: cum paralipomenis historiæ omnium animalium. Bartholomæus Ambrosinus … labore, et studio volumen composuit; Marcus Antonius Bernia in lucem edidit (Bologna, 1642).
Gessner, Conrad, Historiae Animalium, 3 vols (Frankfurt, 1620), volume 1. English translations from Edward Topsell, The Historie of Foure-Footed Beastes (London, 1607).
Jonstonus, Joannes, Historiae naturalis de quadrupedibus libri (Amsterdam, 1657). English translations from Joannes Jonstonus, An History of the Wonderful Things of Nature (London, 1657) and John Johnston, A Description of the Nature of Four-Footed Beasts (Amsterdam, 1678).
Kirchmaier, Georg Caspar, De basilisco, unicornu, phœnice, behemoth, leviathan, dracone, araneo, tarantula et ave paradisi, dissertationes aliquot (Wittenberg, 1669). English translation from Edmund Goldsmid, Un-Natural History or Myths of Ancient Science (Edinburgh, 1886).
Lavers, Chris, The Natural History of Unicorns (London, 2009).
South, Malcolm, ‘The Unicorn’, in Malcolm South (ed.), Mythical and Fabulous Creatures: A Source Book and Research Guide (New York and London, 1987), pp 5-26.
Text: Dr. Elizabethanne Boran, Librarian of the Edward Worth Library, Dublin.
 Translation by Edmund Goldsmid, Un-Natural History or Myths of Ancient Science (Edinburgh, 1886), p. 51.
 Malcom South, ‘The Unicorn’, in Malcolm South (ed.), Mythical and Fabulous Creatures: A Source Book and Research Guide (New York and London, 1987), p. 10.
 Pliny the Elder, Natural History, Book VIII, Chapter XXXI.
 Worth owned the Latin edition of this work: Joannes Jonstonus, Historiae naturalis de quadrupedibus libri (Amsterdam, 1657): the translation is from A Description of the Nature of Four-Footed Beasts, with their figures … written in Latin by Dr. John Johnston. Translated into English by J.P. (Amsterdam, 1678), p. 19.
 Edward Topsell, The Historie of Foure-Footed Beastes (London, 1607), p. 711. Topsell’s text (which was not collected by Worth) was heavily dependent on Conrad Gessner’s Historiae Animalium, which Worth had in a Frankfurt, 1620 edition.
 On this see Chris Lavers, The Natural History of Unicorns (London, 2009).
 Ambroise Paré, On Monsters and Marvels. Translated with an Introduction and Notes by Janis L. Pallister (Chicago, 1982), p. 166. Worth had a 1685 Lyon edition of Les oeuures d’Ambroise Paré.