Clean the mackerel, wash, and wipe dry. Split it open, so that when
laid flat the backbone will be in the middle. Sprinkle lightly with
salt, and lay on a buttered gridiron over a clear fire, with the inside
downward, until it begins to brown; then turn the other. When quite
done, lay on a hot dish and butter it plentifully. Turn another hot
dish over the lower one, and let it stand two or three minutes before
sending to table.