Divide butter in 3 parts. Put one piece of butter, with lemon juice and egg yolks in the top of a double boiler. Cook over boilig water, stirring constantly with a wire whisk. As the butter melts, add a second piece. As mixture starts to thicken, add the third piece of butter. Add the water and cook for 1 minute. Remove from fire and add seasonings. Should the mixture curdle, add 2 Tbsp boiling water, drop by drop.

Cook Book - Fine Old Recipes, Culinary Arts Press, 1936.