Heat oven to 425 degrees F.
Thoroughly wash and dry potatoes; be sure to remove any eyes. Grease lightly. The easiest way to do this is to grease or oil the palms of your hands and then transfer the grease to the potatoes.
Spread potatoes out on top oven rack, taking care not to burn your hands. Bake until tender when squeezed or tested with a fork, about 40 to 60 minutes, depending on size of potatoes.
When potatoes are done, remove from oven, split open and top with a lump of butter. Season to taste with salt.
Craig Claiborne, The New York Times Cook Book, 1961http://macheads2.net/recipes/BakedPotatoes.html