In a very old post somewhere, someone recommended White Mountain Cream Frosting and gave the recipe. I don't quite understand it [my questions are in square brackets]:

1 cup sugar
1 teaspoon vanilla or
1/3 cup cold water
1/2 tablespoon lemon juice
White 1 egg

Put sugar and water in saucepan, and stir to prevent sugar from adhering to saucepan; heat gradually to boiling-point, and boil without stirring until syrup will thread

[What temperature? Does this mean thread stage 230° F235° F?]

when dropped from tip of spoon or tines of silver fork.

[Silver? Does it have to be sterling? What about the spoon?]

Pour syrup gradually on beaten white of egg,

[So, was the first thing in the instructions supposed to be "beat the egg white to -- what? -- just a little? soft peaks? stiff peaks?" Or "beat the egg white while the sugar is cooking"--then again, just a little? a lot?]

beating mixture constantly, and continue beating until of right consistency to spread; then add flavoring

[Does this mean just extract? What about liquer? Other ways of flavoring? What about coloring?]

and pour over cake, spreading evenly with back of spoon. Crease as soon as firm.

[What does "crease" mean here? Is there a picture anywhere that shows this creasing?]

If not beaten long enough, frosting will run; if beaten too long, it will not be smooth. Frosting beaten too long may be improved by adding a few drops of lemon juice or boiling water. This frosting is soft inside, and has a glossy surface. If frosting is to be ornamented with nuts or candied cherries, place them on frosting as soon as spread. {end of recipe}

Can anyone help me understand this? Thanks.

Shanter