From 1918:

1 glass cider
1 egg yolk
1 egg white
2 tablespoonful granulated sugar
1 teaspoonful powdered sugar

Beat egg yolk until light; add sugar and cider; beat well. Pour into glass containing a piece of ice. Put the beaten white of egg, which has been sweetened with powdered sugar, on top. Dust over with grated nutmeg.
Opportunely comes this temperance eggnog as a suggestion for war times and prohibition districts.
Many are joining the boys in khaki in their enforced abstinence, both as an economic measure and as a matter of comradeship.