This section is from the book "Philadelphia Cook Book: A Manual Of Home Economies", by Sarah Tyson Heston Rorer. Also available from Amazon: Philadelphia Cook Book.
Put two quarts of raspberries into a stone jar, and pour over them one quart of good cider vinegar. Cover and stand aside for two days, then drain off the liquid without mashing the berries, pour it over a quart of fresh fruit, and stand as before. Do this once more, the last time straining through a muslin bag. Now add one pound of sugar to every pint of this liquid. Boil slowly five minutes, skim, let stand fifteen minutes, bottle, and seal.
Strawberry and blackberry vinegars are made in precisely the same manner.