My grandmother checked the oven temperature by holding her hand in the open oven. The oven temperature was defined as slow to very fast. That discribed how long it took to be too hot to hold your hand in the oven. My mother got a stove with an oven that had a knob with marks on it for every 25 degrees. She had to check it with an oven thermometer. Both of those women made excellant bread. I have seen bakers throw a small handful of cornmeal onto the hearth to check the oven heat. Today we have digital controls on our ovens but are they more playthings than truly useful tools?