Kelim, Chapter Twenty-Seven, Mishnah Five
1) Worn-out pieces of a sifter or a sieve that were adapted for use as a seat:
a) Rabbi Akiva rules that they are susceptible to uncleanness,
b) But the sages rule that they are not susceptible unless their rough ends were cut off.
2) A child’s stool that has legs, even though it is less than a handbreadth high, is susceptible to uncleanness.
3) A child’s shirt:
a) Rabbi Eliezer rules it is susceptible to uncleanness at any size.
b) But the sages rule: it is susceptible only if it is of the prescribed size, and it is measured when doubled over.
Section one: If one takes a worn-out sifter or sieve and cuts a piece out of it to use as a seat (not really sure how comfy this must have been, but what do I know?), Rabbi Akiva says that it is immediately susceptible to impurity. The other sages say that before it can be considered a seat he must cut off the rough edges (see 20:4 for a similar dispute).
Section two: A child’s stool (meaning chair, not the other kind J) need not be one handbreadth high to be susceptible to impurity.
Section three: According to Rabbi Eliezer, a child’s shirt can be of the smallest size and still be susceptible because it is considered a vessel.
The other sages say that even a child’s shirt must fulfill the minimum sizes mentioned in mishnah two. If it is made of cloth, it must be three handbreadths square and it is measured on each side, i.e. the front must be three by three and the back must be three by three as well.