Baking soda (you can get 5 pounds for about $5 at bulk stores like Smart & Final) - about 1 cup into the bathtub

And,

Epsom Salts - about 1 cup into the bathtub


The baking soda absorbs into the skin and helps neutralize excessive acids (which just about everybody has if they are eating much cooked food at all), and together with the Epsom Salts - I get out and my muscles are completely transformed into a state of deep relaxation!