Shabbos, Mishnah 3. This Mishnah discusses how to treat various items lying on the table which are fit for animal consumption, and what their status is regarding muktzeh and carrying on Shabbos.
Bones and peels:
The Mishnah states that one may pick up and clear away from the table "atzamos u'kelipin" - bones and peels. This refers to bones that are fit for dogs to eat, which therefore have the status of animal food, and likewise to peels that are also eaten by animals. For this reason one may remove them directly, and they are not muktzeh.
Beis Shammai say that one must take the entire table, tilt it on its side and shake these items off it, but one may not move them directly. According to this view these items are considered muktzeh and may not be handled by hand, yet moving them by means of the table is permitted.
Some understand that the Mishnah is dealing with items that are not fit for animal consumption, and the dispute concerns them: one opinion holds that this category of muktzeh is not forbidden, while Beis Shammai hold that it is forbidden. It is worth noting that in the Gemara the names of the disputants appear in reverse: Beis Shammai are the ones who say that one must lift the table and not the items themselves, while Beis Hillel permit moving them directly.
The Mishnah continues and lists additional items that may be cleared from the table, since they are not muktzeh and their status is that of food fit for animals:
Pieces and crumbs of bread that are less than the measure of a kezayis.
Pods of a particular type of legume.
Lentil husks.
The sponge and the prohibition of squeezing:
From here the Mishnah moves to a different type of object, and to the matter of squeezing on Shabbos. The case is a wet sponge:
A sponge that has a leather handle: one may wipe up liquids with it - not to squeeze it out, but only to absorb with it - since handling it by means of the handle does not cause any liquid to be squeezed out.
A sponge that has no leather handle: one may not wipe with it, since by its very nature the mere touching of it, moving it or absorbing with it causes liquid to be squeezed out of it.
The Mishnah further states that whether it has a handle or does not have a handle, if it is dry it may be moved on Shabbos, since it has the status of a utensil.
Even so, the sponge itself is not susceptible to tumah. This is not because it is not a utensil, but because the material from which it is made is not among the materials that are susceptible to tumah.