There are instances in which [the Sages] spoke of a large measure: A ladleful of corpse-dust [is measured against] a full, big physicians’ ladle. The split bean of negaim [is measured against] a split Cilician bean. One who eats on Yom Kippur the volume of a large date [is liable if he ate] the equivalent of it and its pit. The measure of skin-bottles of wine and oil [to lose their tumah] is [a hole] the size of their large whorl. [Regarding] a window that was not made by a person, its measure [to spread tumah] is the size of a large fist; that is, the fist of Ben Battiach. R’ Yose said: [That fist] has [the same proportions] as a large human head. [Regarding a window] that was made by a person, its measure [to spread tumah] is the size of [the hole made by] the large auger of the [Temple] chamber. This is [as large] as an Italian pundyon, and [is also as large] as a Neronian sela; and [is also as large] as the hole

All [utensils made from] sea [creatures] are tahor except [utensils made from] a “sea-dog,” since it flees to dry land. These are the words of R’ Akiva. If one makes utensils from something that grows in the sea and attached to [the utensils] something that grows on land, even a thread or a string, something that is susceptible to tumah, [the utensil] is [susceptible to] tumah.