eggshellful
The amount contained in an eggshell
Beat the white of one egg until stiff, add 1/2 of an eggshellful of cream and beat together well, add enough pulverized sugar to harden it so as to form in squares lay on pasteboard to harden.
Where it comes from
From Middle English egschelfull, egge schellefull, egge schelle ful, equivalent to eggshell + -ful.
Adapted from the Wiktionary entry eggshellful (CC BY-SA 4.0).