Doesn't the "pinch of salt" thing actually mean something different though? My mom always said a pinch was about a quarter teaspoon, so it was a real amount, just measured with your fingers instead of a spoon. She had small hands and her pinch was different from my dad's, which is why her bread always came out better than his. So I don't know that it was advice about feeling your way through a recipe, it might have just been how people wrote down small amounts back then. Not trying to nitpick your grandma, but the card probably meant more than a lesson in instinct.