Plain Icing

This is an uncooked egg-white icing, and that is the problem with it: the whites are never heated at any point, and the finished icing is then left to stand at room temperature on a cake. The notes below explain the terms and the failure points rather than offering a way around them.

• Raw egg white, never heatedThe whites go on the cake raw and stay raw. Salmonella in shell eggs is a surface and occasionally internal contaminant, and beating whites to a froth does nothing to it; an icing left in a "cool spot" or on a cake for a day is a hospitable medium. Use a current recipe built on pasteurised whites, meringue powder, or a cooked sugar syrup instead.
• The stray last line"1 cup sugar ½ cup water" belongs to no step in the method, and there is no instruction anywhere in the text telling you what to do with it. It may be a fragment of an adjacent recipe, but nothing on the page confirms that.
• What "powdered sugar" meantIn North American books of this period powdered sugar was usually a fine-milled granulated sugar, coarser than today's confectioners' sugar and without cornstarch in it. Modern confectioners' sugar is not a like-for-like swap by volume, and the anti-caking starch changes how the icing sets.
• "Flavoring" and its strengthA teaspoon of unspecified flavouring would most likely have been vanilla, lemon, almond or rose. Period extracts varied widely in strength and composition, so a modern teaspoon is not necessarily an equivalent measure.
• Ratio and coverageTwo whites to a cup and a half of sugar gives a soft, spreadable icing rather than a stiff piping consistency. The original gives no yield.
• Why the recipe insists on speedWhy the recipe mentions using it at once -- An uncooked white-and-sugar icing weeps and separates as it stands, as the sugar draws water out of the foam. The recipe nonetheless permits holding it in a cool spot.