The non-fiction book Shadows in the Sun
by Wade Davis contains the following passage:
There is a well known account of an old Inuit man who refused to move into a settlement. Over the objections of his family, he made plans to stay on the ice. To stop him, they took away all of his tools. So in the midst of a winter gale, he stepped out of their igloo, defecated, and honed the feces into a frozen blade, which he sharpened with a spray of saliva. With the knife he killed a dog. Using its rib cage as a sled and its hide to harness another dog, he disappeared into the darkness.
This caught the attention of some archaeologists who decided to test if a knife made from human feces would actually be strong enough to cut through muscle and tendons. They published their results in the Journal of Archaeological Science.
The researchers paid close attention to detail. For instance:
In order to procure the necessary raw materials for knife production, one of us went on a diet with high protein and fatty acids, which is consistent with an arctic diet, for eight days.
However, the results were disappointing: "the knife-edge simply melted upon contact, leaving streaks of fecal matter."
Conclusion: the story of the fecal knife was an urban legend.