The Picador appears in the 1937 Café Royal Cocktail Book with tequila, Cointreau, and fresh lime or lemon juice in a 2:1:1 ratio. Its printed preparation instruction is “Shake.” This documents a historical recipe; it does not establish a direct line of influence on the margarita.
The original instructions for the Picador in the 1937 publication were, "Shake".
Notes
Ratio: 2:1:1 (Tequila : Cointreau : Lime or Lemon Juice).The 1937 source permits either fresh lime juice or fresh lemon juice. The displayed Flavor Key describes the lime-juice version.