How to Make a Flaming Drink, 1862

bartender with fancy mustache pouring flames from one mug to another

Blue Blazer. (Use two large silver-plated mugs, with handles.)
1 wine-glass of Scotch whiskey.
1 do. [ditto = the same amount] boiling water.
Put the whiskey and the boiling water in one mug, ignite the liquid with fire, and while blazing mix both ingredients by pouring them four or five times from one mug to the other, as represented in the cut. If well done this will have the appearance of a continued stream of liquid fire. Sweeten with one teaspoonful of pulverized white sugar, and serve in a small bar tumbler, with a piece of lemon peel… The novice in mixing this beverage should be careful not to scald himself. To become proficient in throwing the liquid from one mug to the other, it will be necessary to practise for some time with cold water.

Jerry Thomas, How to Mix Drinks: Or, the Bon-Vivant’s Companion

The splendid mustache is a prerequisite, but be careful not to ignite it while mixing this manly drink.