Right you are. The 4 things mentioned at cayceconcepts.com are: Water, Salt, Soda, and Iodine.
I had wondered about the soda myself. It would be good to know exactly if baking soda is what he was referring to when he said these four items. I spent a little time at the cayce website: A.R.E., I believe is the name, and he does mention the Sodium Bicarbonate several times, which is the only ingredient in baking soda.