So far as I know, the oldest in the English language at least, is Banting's Letter on Corpulence. Having lost weight and dramatically improved his health on a low carbohydrate diet. Banting wrote and self-published the book back in the Mid-Victorian era, and he distributed it for free.
Read More »Potato Substitutes on Low Carb? by Dana Carpender
Sadly, Ketatoes are no longer with us, though I still have a stash I hoarded when the Keto company went under. There is a substitute: Dixie Diners Instant Mashers. I've tried them in several of my recipes, and they work just like the Ketatoes mix.
Read More »