I remember reading an old parable about a woman who always cut off the ends of her meatloaf before serving it. At one point someone asked her why she did that, and she said that her mother had always done it that way. So she went to ask her mother, and got the same answer. The two of them went to the woman’s grandmother who said that the serving plate she cooked the meatloaf was too small, so she cut off the ends to…
Primo Levi told a similar story about tracking down the source of a lacquer recipe when he was working at a paint factory. There was a point in the recipe where the instructions called for adding half an onion into the vat of lacquer. As a chemist, he was fascinated by this because he could not think of any way the chemicals in the onion, in that quantity, could affect the end product. He eventually found a retired employee living nearby who was able to explain that the onion was used to check the temperature of the lacquer. When the onion started to bubble, the mixture was hot enough to proceed to the next step. By the time Primo Levi was working at the plant in the 1940s, the plant had upgraded to modern equipment with integrated temperature gauges, but the onion remained in the recipe.