Daly's Bartenders' Encyclopedia by Tim Daly (1903, p.121)

1 spoonfulcocoa — Baker's cocoabase
jiggercognac — OCR obscures the exact fraction before jigger; preserve as uncertain.base
1 jiggerSt. Croix rum base
milk — hot milkdilution
1 spoonfulsugar — Dissolve in a little hot water.sweetener
  1. Put the cocoa, sugar dissolved in a little hot water, Cognac, and St. Croix rum into a large china mug.
  2. Fill with hot milk, stir well, and serve with a spoon.

Daly calls it a recent cold-weather resuscitator and nourishing stimulant.

See also: After-Dinner Companion, Hot Milk Punch