This section is from the book "The American Woman's Cook Book", by Ruth Berolzheimer. Also available from Amazon: The Domestic Arts Edition of the American Woman's Cook Book.
For boiling a large fish whole, a fish-kettle with strainer, a large kettle with a wire frying-basket or a steamer is needed. A plate in a piece of coarse muslin or cheese-cloth, kept for this purpose, may be used for fish in small pieces. Clean the fish, rub a little salt over it, wrap it in a cloth and place it in the container in which it is to be boiled or steamed.
The fish must not be put into cold water, as that extracts the flavor, nor into boiling water, as that breaks the skin, but should be put into hot water, which may then be quickly brought to the boiling-point. After the water boils, decrease the heat so that it will simmer.
Use enough water to cover the fish, add one teaspoon of salt and one tablespoon of vinegar or lemon-juice to every two quarts of water. These whiten the flesh and make it firm as well as season it. After the water begins to simmer, allow five to ten minutes to the pound for small thin pieces and ten to fifteen minutes to the pound for large thick pieces.