The No. 4 - as made famous at Eastern Standard in Boston, MA - is meant to be the polar opposite of a Corpse Reviver No. 2. Basic in creation, but complex in depth and flavor, it's not for the faint of heart... but will win over even the most discerning of folks who fancy themselves experts with heightened palates.
1 oz Rittenhouse Rye
1 oz Fernet Branca
1 oz Yellow Chartreuse
3 dashes Mole Bitters
Combine ingredients and stir over ice. Strain into rocks glass, garnish with lemon peel. Dispose of garnish.