What is the history of beating egg whites? How did they do it before the ‘egg beater’ was invented?
If you mean before electric egg beaters, they beat them by hand. In the last installment of the Little House on the Prairie series, Laura and Ma are baking her wedding cake. “The whites are stiff,” Ma pronounces. Laura responds, “My arm is stiffer,” rubbing it.
As far as the “manual” egg beater is concerned, I would imagine that it was invented at the same time that cooks decided it was necessary to beat egg whites.
What fancy item are you referring to? The electric mixer? Wire whisks have been around for a long time. Forks and spoons can perform the same task.
It just takes longer.