Wash and rinse the peanuts at least 3 times to remove any excess dirt. In a large stockpot, add the peanuts. Make a note of where the top of the peanuts are in the stockpot before you add the water. Add enough water to come up 1 inch above where the peanuts were (they float as you add the water). Then add the salt.
Bring to a boil, reduce to a simmer and cover. Simmer until tender and soft (and not crunchy), about 6 hours, adding water as needed and stirring periodically.