I don't know. I just learned it in school in a not-very-useful home economics class in a public school. This was around 1990 (give or take a year, as I'm not su

I don't know. I just learned it in school in a not-very-useful home economics class in a public school. This was around 1990 (give or take a year, as I'm not sure what grade I was in at the time). I've never needed the information. It is probably very easy to stumble upon the information now just by consuming popular culture stuff. This sort of information was probably everywhere in Hoover's time. Women's magazines would have featured such things for the middle class to consume, and some of the poor folks had to know because they worked in upper-class homes and restaurants.