The recipe that carryover below is taken from Science in the Kitchen and the Art eating well, famous text of the gastronome Pellegrino Artusi.
It is a dolce: jelly orange frost.
This is what is written:
“Sugar grams 150, isinglass grams 20, water ounces 4, Alkermes 4 spoonfuls, Rum 2 spoonfuls, a big sweet orange, a lemon.
Put glue in springs and changing once the water, lasciatevela for an hour or two.
Boil the sugar in half above water for 10 minutes and pass it to a diaper.
Squeeze in this siroppo orange and lemon, by passing the sauce from the same diaper.
Take away the already found glue and then to lift the boil water in the two deciliters remained and pour this also in said siroppo.
Add to the same Alkermes and Rhum, stir everything and when it starts to cool pour it into the mold held in the summer and ice in cold winter.
The molds of this kind of desserts are all made in copper spiers, some with a hole in the middle, others without, in order to obtain a good effect on the table.
For isformarla good grease lightly, before pouring the mixture, the mold with oil and then dip it for a moment in hot water or wipe it with a rag boiling.
Isinglass is not harmful, but it has the disadvantage of being able somewhat heavy stomach” (Photo gives: nonsprecare.it).