Sufficient vinegar to cover the mushrooms

From 1922:

Sufficient vinegar to cover the mushrooms; to each quart of mushrooms, 2 blades of pounded mace, 1 oz. of ground pepper, salt to taste. Choose some nice young mushrooms for pickling and rub off the skin with a piece of flannel and salt and cut off the stalks if very large. Take out the red inside and reject the black ones, as they are too old. Put them into a stewpan, sprinkle salt over them, with pounded mace and pepper in the above proportion; shake them well over a clear fire until the liquor flows, and keep them there until they are all dried up again; then add as much vinegar as will cover them; just let it simmer for 1 minute, and store it away in jars for use. When cold tie down and keep in a dry place.