Libro de Cocktail by Juan A. Lasa (1929, p.7)

1 portionAbsinthe — Ajenjobase
2 dropAngostura bitters — Amargo Angosturabase
  1. Shake the bitters and absinthe with finely crushed ice.
  2. Strain into a chilled long cocktail glass.

Ice: Crushed ice

The source defines one portion as the small glass normally used to serve rum.