Cut pulp from watermelon rind, leaving a small amount of red pulp on rind. Reserve pulp for another use. Cut rind into 1-inch cubes, and place in a large bowl.
Stir together salt and 2 quarts water. Pour over rind. Cover and chill 8 hours. Drain; rinse well.
Combine rind with water to cover in a Dutch oven. Bring to a boil; reduce heat, and simmer, uncovered, 10 minutes or until tender. Drain.
Combine remaining 2 cups water, vinegars, and next 5 ingredients in Dutch oven or very large saucepan. Bring to a boil; reduce heat, and simmer, uncovered, 20 to 25 minutes or until mixture becomes a thin syrup. Add rind, and simmer 5 to 6 minutes or until rind becomes translucent.
Pack hot rind mixture into hot jars, distributing lemon and spices evenly and filling to 1/2 inch from top. Remove air bubbles; wipe jar rims. Cover at once with metal lids, and screw on bands. Process in boiling water bath 20 minutes.