Julian's Recipes by Julian Anderson (1919, p.17)

0.5 tablespoonfulsugar — Or half lump/cube; dissolve in a little cold water.base
1 ponywhiskey, brandy, or gin base
  1. Dissolve the sugar in a little cold water in a whiskey glass.
  2. Add the spirit, stir with a spoon, and serve.

See also: Hot Toddy, Hi Ball

Source says either whiskey, brandy, or gin.