see For a soft-boiled egg, place egg in rapidly boiling water and boil from three to five minutes. For hard-boiled EGGS, place in rapidly boiling water and boil twenty minutes, or cover with boiling water and cook in the double boiler one hour. For a soft-cooked egg, not boiled, place egg in a small Saucepan of boiling water, cover, and let stand on back of range from six to eight minutes, when the albumen should be evenly coagulated throughout. The time for cooking in this way will depend upon the number of EGGS to be cooked, the size of the Saucepan, and the amount of boiling water. For uniform results, use medium-sized EGGS, cook in the same pan, and measure the quantity of water each time. Thus you can find the exact time required to cook the EGGS as desired.
http://lostpetfoundpet.com/table-of-contents/ Better Meals for Less Money, by Mary Green (Year 1909)