Orange Marmalade

From 1911:

Take five good sized oranges and two large lemons. Slice them, peeling and all, removing the seeds. Add to these three quarts of water, bring to a boil and allow to boil briskly half an hour. Then add three quarts sugar and boil for three-quarters of an hour, remove and pour into jelly glasses. It will be thick and delicious, and this amount will make about 16 glasses.