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.
Select for these mangoes fully matured green tomatoes. Cut a slice off the stem end and remove the seeds and part of the pulp, leaving good-sized cavities in each tomato. Fill these cavities with chopped cabbage, onions, celery and a little horseradish, pack in as solidly as possible, and then fasten on the slice that has been removed; this can either be tied on with strings, or kept in place by means of splints cut from stick cinnamon. Cover these stuffed tomatoes with a strong brine, and let them stand in it overnight, then drain off. Parboil in water to which has been added a pint of vinegar. Remove and drain.
To each seven pounds of the tomatoes use four pounds of sugar, one quart of vinegar, one pint of water, and two ounces of mixed spices. Pack the mangoes in stone jars, and pour the boiling hot vinegar syrup over them. Allow to stand for twenty-four hours, pour off the vinegar, and boil again until about the consistency of honey; then pour it over the mangoes again. Keep tightly covered.