A basic baheres is the size of a Cilician gris squared. The area of a gris is equivalent to nine lentils. The area of a lentil is equivalent to [the area on which] four hairs [grow]. Thus, there are thirty-six hairs [in a nega].

A baheres the size of a gris that contained a michyah the size of a lentil — [if] the baheres spread, it is tamei; [if] it receded, it [becomes] tahor. [If] the michyah expanded, [the baheres] is tamei; [if the michyah] receded, [the baheres] is tahor.