This drink was a favorite of American expats during Prohibition. Prior to then it was known as the Milano-Torino, for the cities where its two main ingredients were first made: Milan (Campari) and Turin (sweet vermouth).
As the story goes, Ernest Beaumont-Gantt created this potent drink in the 1930s and named it for its mind-altering effect after a friend consumed three of them. This lower-proof version is made with Velvet Falernum, an almond-and-lime-flavored liqueur that's a key ingredient in many tiki drinks.
The best kind of cola to use in this drink is Mexican Coca-Cola (available atamazon.com) or another brand made with cane sugar. Sugar-based colas have a crisper, cleaner flavor than the more readily available ones made with high-fructose corn syrup.