Jai Sri Ram,
The Hill on which Sri Hanuman planted his foot while keeping sank down immediately,
Sri Hanuman Sped forth in the same way as the unerring shaft of Sri Rama, knowing him to be the emissary of sri Ram, the presiding deity of ocean Said to mount Mainaka to raise above to the level of Sri Hanuman and relive him of his fatigue,
In the past times mountains had wings and could fly like birds but this was against the spirit of nature to main stable pace on the earth,
Indra, the king of gods clipped the wings of all mountains by his thunderbolt and since then they become stationery but Mainaka was competent enough to safeguard self by taking refuge in ocean, even otherwise this Mainaka was elder brother of Devi Parvati,
May Lord bless all,
Thanks Please