1 1/2 ounces bourbon whiskey
1 ounce Campari
1 ounce sweet vermouth
Garnish: lemon twist
Stir with ice, and strain into a cocktail glass.
Source: "Barflies and Cocktails" (1927)

Essentially a "Bourbon Negroni". It originally appeared in "Barflies and Cocktails" (1927) using equal parts of all three ingredients. Boosting up the bourbon helps to make a more balanced cocktail.