"To make mulsum...you put 10 librae of best honey into an urna of must and after mixing them carefully together, you store the must in a flagon and immediately seal it up with plaster and order it to be placed in a loft [to ferment for a month]." (Columella, On Agriculture XII.xli)
The Romans had their list of cherished wines—most of them, such as Falerinian, from the Campania and Latium, south of Rome—and almost all of them white and sweet: some, such as raisin wine (passum), were quite potent (see Columella, On Agriculture XII.xxxix). See White and Sweet. They did not hesitate to sweeten a wine even further, by mixing in honey either during its original fermentation or directly before drinking it. They also seem to have been ever-willing to experiment with adding herbs to the wine as an artificial flavoring. In some instances, the herbs served to mask the failings of an inferior wine; other times they were intended to re-awake jaded taste buds in the fickle popular marketplace.