Ctesias (fifth century BC) recounted contemporary Persian beliefs of white Indian animals which had a white horn, black in the centre and flaming red at the pointed tip, projecting from their forehead. Reinforced by classical and medieval writers, travellers, biblical warrant and trade in narwhal tusk, the unicorn became firmly established in European mythology. Increasing popularity as an alexipharmic, prophylactic and counter-poison through the fifteenth to seventeenth centuries led to rising demand and rapidly inflating prices. Debate raged as to which was the ‘true unicorn’ (Unicornum Verum), narwhal tusks or mammoth ivory (Unicornu Fossile); shavings...