Take the red part of the watermelon out. Peel the hard part off outside. Take the middle of the rind and cut up into 1 to 2 inch slices. Put in salt water and soak overnight. The next morning, drain salt water off. Cook them in clear water until they are tender. Drain that water off. Put 3 cups of white vinegar, 3 cups of sugar, 1 teaspoon of cinnamon and a heaping teaspoon of mixed pickling spice and 1 cup of water into a pot. Bring to a boil, add the rind to the syrup and cook until clear and glassy. Pack in jars and seal.