(Image: Bridgeman Art Library)
Before ships had refrigerated morgues, it was common to bury the dead at sea. A sailor's body and weights would be sewed up inside a hammock. His mates would finish the task by sewing the last stitch through the dead man's nose--to be certain that he was really dead.
Here's a description provided by one sailor from his experiences in the 1960s:
The mate sent me down to assist the bo'sun to prepare and stitch up the corpse, as he said I would be unlikely to witness such an occurrence again. The bo'sun, a North Sea Chinaman (ie, he hailed from the Orkney Isles), was in his sixties and had performed the task several times before. He was a deft hand with the palm [leather glove] and needle used to sew the heavy canvas into a shroud around the body, and when he came to the final stitches around the face he pushed the large triangular-shaped needle right through the nose. I winced, and he looked up at me and said, "That's the law of the sea, the last stitch through the nose, if that don't wake him up I know he's dead."
Apparently, it was not uncommon for sailors or passengers to be mistakenly pronounced dead. This was the final test.