One of the earliest examples of a smash appears in the form of a Julep recipe in Jerry Thomas' 1862 How To Mix Drinks, or, The Bon Vivant's Companion. Though Thomas doesn't mention the smash by name, his definition of the Julep clearly lays the foundation for the future of the category.
1.5 oz Rendezvous Rye
1 Lemon wedge
3-4 mint leaves
0.25 oz Simple Syrup
In a shaker, muddle 1 lemon wedge, 3-4 mint leaves and 0.25 oz of simple syrup together. Add 1.5 oz Rendezvous Rye and ice. Shake and strain over a rocks glass filled with crushed ice. Garnish with a mint sprig and lemon wheel.