The Bread And Biscuit Baker's

Here are few paragraphs from the book,

To make this take 2 lbs. of finely powdered icing sugar (first having an earthenware pan made warm), put in six fresh whites of eggs, and immediately whisk them, and as quickly as possible, until quite stiff; then add the sugar by degrees, whisking all the time. As soon as it appears light cease whisking, and beat it well with the spatter until you have put in all the sugar. A little tartaric acid or lemon-juice may be added towards the end of the mixin...