Yosef Karo, Translation:Shulchan Aruch — Orach Chaim 368…
“ Paragraph 3 - What is the required initial size for an eruv? When eighteen or fewer people make the eruv, it must be the equivalent of a fig for each person. If they are more than eighteen, even if they are more than one thousand [people] , the required size is the equivalent of two meals, which is eighteen figs or six eggs. ”
