In Ariosto's epic 16th-century poem Orlando Furioso, the beautiful Angelica, chained, naked, to a rock and menaced by a sea monster is rescued by the valiant Ruggiero, riding a 'hippogriff', the offspring of a griffin and a mare — an entirely imaginary winged creature (as readers of Harry Potter know). Volatore, as this hippogriff calls himself, has escaped the poem in which he has been confine...