This section is from the book "Mrs. Rorer's Vegetable Cookery And Meat Substitutes", by Sarah Tyson Rorer. Also available from Amazon: Mrs. Rorer's Vegetable Cookery And Meat Substitutes.......
Boil four good-sized potatoes. While these are boiling cut a good-sized onion into very thin slices; put it in a bowl with a teaspoonful of salt, a saltspoonful of pepper and six tablespoonfuls of olive oil; mix until the salt is dissolved; then add two tablespoonfuls of vinegar. When the potatoes are done, slice them while hot into this mixture, toss carefully without breaking the potato, and stand aside to cool. When cold, turn out on a small platter and garnish with parsley and finely chopped pickled beets.