Jam of Greengages

From 1861:

Put ripe greengages into a kettle, with very little water, and let them stew soft; then rub them through a sieve or colander, and to every pint of pulp put a pound of white sugar, powdered fine;
Then put it in a preserving kettle over the fire, stir it until the whole is of the consistency of jelly, then take it off; put the marmalade in small jars or tumblers, and cover as directed for jelly.
Any sort of plums may be done in this manor.