And there are some things that were created

on the first day [of Creation] that are [susceptible to] tumah (such as earthenware or metal, which are made from the earth),

on the second (i.e. the sky) that that is not [susceptible to] tumah,

on the third day that are [susceptible to] tumah (wooden utensils, which come from trees),

on the fourth (heavenly bodies) and fifth (fish or fowl) that are not [susceptible to] tumah

except for [by rabbinical decree] the wing of the osprey (lest they be confused with the bones of other animals)

and the plated egg of an ostrich (as these eggs were already more durable than most);

Rabbi Yochanan ben Nuri says,

"What is different about the osprey's wing

from all wings" (he held that utensils made from the wing of any bird was susceptible to tumah);

וכל שנברא ביום השישי

and all that was created on the sixth day (i.e. animals)

are tamei.

פרק יז משנה טו

One who makes a receptacle [of wood or leather],

in any case (even the smallest size)

it is tamei.

One who makes a bed or a seat

in any case (i.e. anything made to bear a person's wieght)

it is tamei.

One who makes a pouch from untreated hide

or from papyrus

it is tamei (even though these are no the most durable of materials).

A pomegranate,

an acorn,

and a walnut

that children hollowed out

to measure with them dirt,

or if they were prepared to be the pan on a scale,

it is tamei,

as they [the children] have a deed

[even if, in other respects,] they do not have intent.