I was thinking that most recipes for a while were handed down, or communicated like folk-lore, but at some point someone decided to write them down and sell them for money. When did that happen?
People have been writing down recipes for millennia, we even have an ancient Mesopotamian recipe for hippo soup that's around 6000 years old!
But the first modern cookery books, aimed at the general public and sold in vast quantities, did not arrive until the mid 19th c.
The most famous of these early works were Elizabeth (Eliza) Acton's 'Modern Cookery for Private Families' and Isabella Beeton's 'Mrs Beeton's Book of Household Management'
Although, not strictly a cookery book as it covered many other aspects of housekeeping, Mrs Beeton's work, which was serialised before being published as a single book, contained over 1000 pages of recipes. Eliza's book pre-dated Isabella's by a short while and set the standard for recipes aimed at the general public by including exact measurements, timings and notes on methodology.
Prior to this recipes were usually aimed at professional cooks or chefs who would be expected to already have some expertise and so they would be usually be more vague.
http://en.wikipedia.org/wiki/Modern_Cookery_for_Private_Families
http://en.wikipedia.org/wiki/Mrs_Beeton%27s_Book_of_Household_Management
http://www.handmadecharlotte.com/healthy-hungry-hippo-soup-recipe/