What was Hanuman's Speed ?

The mythologies are filled with people of superhuman powers. So in Ramayana we have Ravan with 10 heads and Hanuman who could fly from Lanka to the Himalayas. The fact is if such people existed, how come we don’t have 10 headed people now ? A Berkeley Professor has got interested in finding the truth behind all these symbols.

Ten-headed demon king Ravana of the Hindu epic Ramayana actually had one head and the other nine were its reflection on the nine large polished gems that he wore around his neck, an American scholar of Sanskrit has reasoned.

In a lecture in New Delhi titled, “How fast do monkeys fly? How long do demons sleep?” where he read commentaries on Sanskrit epic poetry, Goldman said ancient scholars like Nagoji Bhatta, Govindaraja, Maheshwara Teertha, Satyateertha and Madhava Yogendra tried to “track down the narrative” and explain through “scientific reasoning” the seeming exaggerations in the works. [Hanuman flew at 660 km per hour]

How will gems around the neck reflect the head ? And the “scientific” explanation is not on how monkeys could fly, but on how fast he could fly. I wonder what this professor teaches.