The question of how to make mulled wine comes up every now and then. I ran into this recipe in a book "Christmas in the Old West" by Sam Travers and thought I might share it.
Mulled Wine: Grate one half Nutmeg into a Pint of Wine and Sweeten to your Taste with Loaf-sugar. Set it over the fire and when it boils take it off the fire to cool. Beat the yolks of four eggs very well, strain them and add to them a little cold wine, them [sic] mix them with hot wine gradually. Pour it backward and forward several times till it looks fine and light, then set it on the fire and heat it very gradually till it is quite hot and pretty thick and pour it up and down several times. Put it in chocolate cups and serve it with long narrow toast. (1801)