The roc (Arabic rukh) is a traveller's marvel of the medieval Islamic world rather than a cult figure. Its famous appearances are in the voyages of Sinbad in the Thousand and One Nights, where sailors mistake its egg for a great white dome and Sinbad escapes a valley by lashing himself to its leg, and in the report of Marco Polo, who was told that a bird of Madagascar could seize an elephant in its talons, lift it and drop it to its death. Behind the figure lie earlier Persian and Indian giant birds, including the simurgh and echoes of the Sanskrit Garuda.
A later, rationalising footnote attached itself to the legend when Europeans learned of the elephant bird (Aepyornis) of Madagascar, a genuine, gigantic, flightless bird whose enormous eggs survive, an animal far too heavy to fly and quite unable to carry anything, but real enough to be offered as the "kernel" of a story it certainly did not generate.