Don the Beachcomber's Mai Tai, The Original via Common Man Cocktails

Really tasty rum classic

Recipe
1 1/2 oz. Myers's Rum
1 oz. Cuban Rum
3/4 oz. Lime Juice
1 oz. Grapefruit Juice
1/4 oz. Falernum Syrup
1/2 oz. Cointreau
2 Dashes Angostura Bitters
Dash of Pernod Absinth