This account arrived to me through a circuitous route – and it may be best to trace to the path of the account’s publication to contextualize the relation of how unicorns were held at Mecca in 1503.
Ludovico di Varthema (1470-1517) was an Italian who claimed to have traveled across parts of Africa and Asia including Somalia, Egypt, Yemen, India, Malaysia, and Indonesia. He wrote about his travels and published them in 1510 in a book called The Itinerary of Ludovico di Varthema of Bologna (Itinerario de Ludouico de Varthema Bolognese). The book was reprinted several times and eventually translated into other languages.
A Spaniard named Peter Martyr d’Anghiera aka Peter Martyr collected travel narratives and accounts and published them over the course of several years. Eventually all of them were collected together and published as one large edition entitled De orbe novo decades. In 1555, Richard Eden translated and published Peter Martyr in a book entitled The Decades of the Newe Worlde or West India. In 1577, Richard Willes reprinted Eden’s version of Decades and added some supplementary travel narratives and called the work The history of trauayle in the VVest and East Indies, and other countreys lying eyther way. It was in Willes’ 1577 book that I found the account of the unicorns of the Temple of Mecca.