Shabbos, Chapter 8, Mishnah 2. The Mishnah continues to discuss the measures for carrying out various items - the minimum quantity for which one who carries it out on Shabbos is liable.
The measure for rope and reed:
"Hamotzi chevel - k'dei la'asos ozen lekupah" - one who carries out a rope is liable for the amount needed to make a handle for a basket. It was common to make handles for baskets out of rope, and therefore the amount sufficient to make one handle is enough to render a person liable.
"Gemi - k'dei la'asos t'lai lenafah ulekhvarah" - reed grass: the amount needed to make a handle for a sifter and for a sieve, two different types of implements used for sifting. For this purpose they did not use rope but reed, which is a more flexible stalk, and so this is the measure set for this item.
Rabbi Yehudah disagrees and says: "K'dei litol mimenu midah min hakatan" - the amount needed in order to take from it the measurement of a child's foot for the purpose of making a shoe. This measure is smaller, and in his opinion this is the use to which such a stalk was put. Some hold that Rabbi Yehudah disagrees regarding the measure of the rope as well, since rope too can serve that very same purpose.
The measure for paper:
"Neyar - k'dei lichtov alav kesher mochsin" - paper: the amount needed to write on it a tax collector's receipt. A kesher mochsin was a sort of receipt issued by the tax collectors: there was a tax for crossing a river and the like, and the collector would take a piece of paper and write on it a particular letter in an unusually large size, and this served as the sign to the official on the other side that the tax had been paid. That is the measure for which one is liable on Shabbos.
"Hamotzi kesher mochsin":
The Mishnah continues and rules that one who carries out into the public domain the tax collector's receipt itself - the receipt issued by the collector - is liable. At first glance this is puzzling, since we were just told that the measure for paper is the amount needed to write a tax collector's receipt on it. Tosafos explain that the Mishnah means that even if the receipt was written on parchment rather than on paper, and even though the measure for parchment is ordinarily larger - enough to write on it the smallest passage of the tefillin - since it has already been used for a tax collector's receipt, even this small amount is significant.
"Neyar machuk":
Paper whose writing has been erased has lost its usefulness for writing, since the erasure is noticeable and it could be erased again. Its measure is therefore larger than that of a tax collector's receipt, and it is "k'dei lichroch al pi tzelochis ketanah shel palyaton" - the amount needed to wrap around the mouth of a small flask of palyaton, a fragrant oil. This vessel was very small and its mouth extremely narrow, and since they had no stoppers, they would take a used piece of paper and wrap it around the opening. That is the measure for erased paper.
In summary: In this Mishnah we learned the measures for carrying out rope (enough to make a handle for a basket), reed (enough to make a handle for a sifter and a sieve, and according to Rabbi Yehudah, enough to take from it the measurement of a child's foot), paper (enough to write a tax collector's receipt on it), a tax collector's receipt itself even when written on parchment, and erased paper (enough to wrap around the mouth of a small flask of palyaton).