What would your contribution be for a book put together to restart a a civilization?
The title is a bit over dramatic but, per the title, if you could contribute with one piece of knowledge to a book that every single individual should learn from in order to kickstart a civilization, what would be yours?
My personal choice would be the process of soap making, from scratch.
How to get rid of hiccoughs. No one knows this trick! All you need to do is hold the flaps of your ears closed and drink a little water. It works every time!