El Bar Americano en España by Pedro Chicote (1927, p.110)

1 tablespoonazúcar en polvo — Inherited from the Spanish grog formula.base
1 liqueur-glasswhisky — Substitutes for cognac in the Spanish grog.base
agua hirviendo — Used as the remainder of the drink.dilution
1 slicerodaja de limón con clavos — rodaja de limón incrustada de 3 ó 4 clavosgarnish
  1. Prepare the same way as the Spanish grog, substituting whisky for cognac.
  2. Serve hot in the same glass.

Cocktails by Pedro Chicote (1928, p.284) — Whisky

Spanish Grog template — Formula del grog espanolbase
1 copitawhisky — Use whisky in place of cognac.base
  1. Build as for the Spanish Grog, substituting whisky for the cognac.

This matters because Chicote explicitly treats whisky grog as a substitution branch from the core Spanish formula.

Related recipes

See also: Spanish Grog, English Grog

Chicote defines this as the same formula as the Spanish grog with whisky in place of cognac.