There is an account of a whaling ship in 1891 called the Star of The East.
The ship spotted a large sperm whale and sent out 2 boats with harpoons to attack the whale. One of the boats was capsized by the whale and a sailor named John Bartley could not be found. The whale escaped. Later that day, the ship spotted another whale. Again the ship sent out boats to attack the whale. This time they were successful.
The next morning the sailors were cutting up the whale. When they got to the stomach part of the whale they noticed something squirming inside its stomach. They cut into the stomach and out came their lost companion sailor John Bartley. Bartley was unconscious but revived. It took 2 weeks for him to recover from this ordeal. He was able to describe to his shipmates the details of being swallowed by the whale, sliding down its throat into its stomach, and the deep darkness inside the whale. He was able to breath in the whale but said there was incredible heat inside the whale. The sailor suffered not permanent damage from the ordeal other than his skin being permanently bleached white.