This is from Sara Paston-Williams's Beatrix Potter's Country Cooking, Frederick Warne & Co., 1991. Hill Top was Potter's farm and the jam is not from her recipe, but one she "would have liked".
I just think of it as summer fruit jam. I can't truthfully say that this jam is better than strawberry jam or raspberry jam or currant jam, but cooking this makes me very happy.
450 g (1 qt.) redcurrants
450 g (1 qt.) blackcurrants
450 g (1 qt.) strawberries
450 g (1 qt.) raspberries
1 large, dark red, and heavily-scented rose
A little butter or glycerin
150 ml (2/3 cup) cold water
1.8 kg (4 lb/8 cups) granulated or preserving sugar warmed.
Wash currants and remove from stems with a fork. Pick over, hull, quarter strawberries; pick over raspberries. Remove petals from rose and snip off the white petal bases and any green bits.
[will finish typing in after I've picked up supper. Takeout, thanks; it's hot here, and I wouldn't make preserves on a bet.]
Rub the base of a large pan with butter or glycerin [?why?] then simmer currants in water for 15-20 minutes or until tender. Add remaining fruits and simmer until tender. Stir in sugar over a very gentle heat until completely dissolved, then bring to a boil and add rose petals. Boil rapidly until setting point is reached. (3-20 minutes.) [snipped detailed discussion of setting point]
After setting point is reached, skim off scum, pour into clean jars, cover with waxed paper discs, then seal. Makes about 2.7 kg.
When I was a girl, we sealed jellies and jams by pouring molten paraffin on the top. That was always exciting -- on top of the stove you had one cauldron of boiling water with the jars, one of boiling jam, and one of melted paraffin [U.S. for wax]. You ladled the hot jam into the hot jar, poured hot paraffin on top, then put the whole shebang somewhere level to cool. When it came time to eat, you pushed down on one side of the paraffin disk to rock the other side up. We saved the disks from year to year and remelted them.
Nowadays you're supposed to seal all jams and jellies with Ball lids and then hot-water-process them. I don't know if this is because the old process was dangerous (it was) or because the paraffin-sealed jellies sometimes molded or because the hot-sealed jam was actually prone to botulism.