From 1912:

Allow for a quart of jelly about a cupful of dry moss and wash it in five waters after it is measured. Be faithful in this cleansing to get rid of sand and salty particles. Have ready a quart of boiling water, the juice of two lemons, and a cupful of granulated sugar (scant). Flavor with a pinch of cinnamon and a glass of sherry. Soak the washed moss in enough water to cover it well and leave it there for an hour. Have the boiling water upon the range and stir the soaked moss into it with the sugar. Simmer until the moss is dissolved and the mixture is clear. Take from the fire, stir in the lemon and spice, lastly the wine, and pour into molds wet with cold water.
Let the jelly get ice cold and eat with cream. This is excellent for one suffering with a cold or cough, and is very nourishing. If you omit the wine, flavor with vanilla or bitter almond.