From 1843:
Salt fish (meaning cod-fish) should be put in a deep plate, with just water enough to cover it, the night before you intend to cook it; take it from that water before cooking and wipe clean.
It should not be boiled an instant; boiling renders it hard. It should be in scalding hot water two or three hours. The less water is used, and the more fish is cooked at once, the better.
It may then be served upon a napkin, and each one may take his portion and mix for himself, with eggs and butter, or it may be picked fine from the bone and mixed with Irish potatoes and butter. No dish is lighter or more digestible.