The Book of Soyga is a medieval or early modern magical treatise, a copy of which is known to have been owned and (to some extent) studied by the mathematician and magician John Dee (1527 – 1608). The book itself was, to the frustration of generations of Dee scholars, not to be found. Quite recently, however, D. Harkness found copies in the Bodleian Library and in the British Library, filed under its alternate title, Aldaraia.
(via Obscurantist).