Sperm whaling is the hunting of the marine mammals for the oil, meat and bone that can be extracted from their bodies. Sperm whales, a large and deep-diving species, produce a waxy substance that was especially useful during the Industrial Revolution, and so they were targeted in 19th-century whaling, as exemplified in Moby Dick. Sperm oil is no longer needed, but another unusual product, ambergris, is still valued as a perfume fixative. Although the animal is classified as a vulnerable species, aboriginal whaling in limited numbers is still permitted, notably from two villages in Indonesia, for subsistence.