This section is from the book "Philadelphia Cook Book: A Manual Of Home Economies", by Sarah Tyson Heston Rorer. Also available from Amazon: Philadelphia Cook Book.
Put the uncooked yolks of two eggs into a clean, cold soup-dish, beat them well with a silver or wooden fork about one minute; then add a half-teaspoonfnl of salt, a dash of cayenne, and, if you like it, a half-teaspoonful of mustard. Work these well together, and then add, drop by drop, a half-pint or more of olive oil. You must stir rapidly and steadily while adding the oil. Do not reverse the motion, or it may curdle. After adding one gill of oil, alternate, occasionally with a few drops of lemon juice or vinegar. The more oil you use, the thicker the dressing. If too thick, add a half-tablespoonful or more of vinegar, until a proper consistency. More or less oil may be added, according to the quantity of dressing wanted. With care a quart bottle of oil may be stirred into the yolks of two eggs, alternating with a few drops of lemon juice or vinegar, after adding the first gill of oil. It is easier, however, to start with three yolks when making a quart of dressing. In case the dressing should curdle, i. e., the egg and oil separate, which makes the dressing liquid, begin anew at once with the yolks of two eggs in another plate, and after stirring them well, add by teaspoonfuls the curdled mayonnaise, stirring all the while, and then finish by adding more oil as directed.
In warm weather, it will take only one-half the time, if you put the dish in which you make the mayonnaise on a piece of ice, or in a pan of ice-water; the oil and eggs should also be cold.
This dressing, if covered closely in a jar or tumbler, will keep in a cold place one week.