Old fashioned drink on ice with orange zest garnish.
Mark Twain's Favorite Whiskey Cocktail Is A Take On The Old Fashioned
While a traditional old fashioned relies on a simple syrup or a sugar cube and Angostura bitters and is served with an orange twist, Mark Twain was more partial to lemon.
Twain revealed his affinity for this cocktail in an 1874 letter to his wife, where he requested "... Scotch whisky, a lemon, some crushed sugar, & a bottle of Angostura bitters."
Since lemon tends to overwhelm other ingredients, use lemon juice and just enough that it is pleasing to your palate if you want to try Twain's take on this drink.