This section is from the book "Preserving And Pickling", by Mary M. Wright. Also available from Amazon: Preserving and Pickling: Two Hundred Recipes for Preserves, Jellies, Jams, Marmalades, Pickles, Relishes and Other Good Things.
Take nice ripe quinces, pare, quarter and core. To add one-third apples will make this marmalade not so strong, and improve it for many. Place in a baking dish and add a little sweet cider, just enough to about half cover the fruit. Cover and bake very slowly in the oven until the fruit is very tender, adding more cider or water as it is absorbed. When done or tender add three-fourths of a cup of sugar to each cup of baked quince. Cook until it becomes a jelly-like mass, stirring constantly to prevent burning, then turn into glasses. Water may be used instead of the sweet cider if preferred, but the flavor of the cider blends perfectly with the quinces.