Any [food] may be used to make an eruv or a shituf, except water or salt — [these are] the words of R’ Eliezer. R’ Yehoshua says: A loaf is an eruv. Even if it is baked from a se’ah but it is broken, it may not be used for an eruv; a loaf worth an issar, but which is whole, may be used for an eruv.