According to ancient Indian legends, Surabhi was believed to be a treasure in the form of a cow that was churned from the cosmic ocean. This belief originates from Hindu mythology, specifically the story of the Samudra Manthan (churning of the ocean).

Option 1, a wish-fulfilling tree, is not the correct interpretation of Surabhi in ancient Indian legends. There is no association between Surabhi and a wish-fulfilling tree in Hindu mythology.

Option 3, a medicine prepared by Dhanvantri, is also not accurate. Dhanvantri is considered the Hindu god of medicine, but there is no connection between Dhanvantri and Surabhi in this context.

Option 4, an intoxicating drink drunk during religious ceremonies, is also unrelated to Surabhi. Surabhi has no association with an intoxicating drink in ancient Indian legends.

In summary, according to ancient Indian legends, Surabhi is believed to have been a treasure in the form of a cow that was churned from the cosmic ocean during the Samudra Manthan.