Totus enim mundus diversis creaturis plenus est; quasi liber scriptus variis litteris et sententiis plenus in quo legere possumus quicquid imitari vel fugere debeamus.
(For the whole world is full of different creatures, like a book written with various words and full of sentences in which we can read what we should imitate and avoid.)
– Thomas of Chobham (d. c. 1236), Summa de Arte Praedicandi 7.2
The Beastiary, or Beastiarum Vocabulum, is a compendium of beasts, both real and imaginary. They can contain mythological creatures, real animals, rocks and even botanica. They originated in the ancient world, but became quite popular in the middle ages as illustrated manuscripts.
Here are a few fantastic beastiaries for you.
Medieval Beastiary (illuminated manuscript) from the digital collection at the British Library. This priceless baby is in middle english, so unless you have a linguistics degree in medieval language, it might not be such a page turner. Luckily for us, the British Library has provided an inline translation of sorts. Plus, the pictures are pretty!
Da Vinci’s Beastiary
Selections from Leonardo’s Da Vinci’s extremely rare beastiary. (from jstor, you can read online for free, but you need to make an account) Apparently this is the only translation in English, and it is a partial one. According to my research, this text is even rare in Italy, where it originated.
The Early English Beastiary
The Early English Beastiary was originally printed as a part of An Old English Miscellany. This version has side by side translation and is from a thirteenth century verse translation of an earlier Latin Physiologus attributed to Theobaldus.
The Fabulous Natural History of the Middle Ages
originally published as part of The Archaeological Album; or, Museum of National Antiquities, The Fabulous Natural History of the Middle Ages is just a short chapter, but it has good info on the unicorn, the mandrake and the elephant.