Mishnayos Orlah Perek 3 Mishnah 2

מלא הסיט – it is according to the suspension between the fore-arm to the finger – all what he is able to widen it, and the suspension that is between the thumb to the finger, all that he one is able to widen it, which is a double “sit” (the double size of the “sit” – the distance between the tip of the thumb and that of the index finger when held apart, or between the root of the thumb and the tip of the index finger, when the former is leaning against the latter – see also Tractate Shabbat, Chapter 13, Mishnah 4), because it is double from what lies between the forearm and the finger. And within the distance of a “sit” is an important measurement for prohibition. Therefore, when they have weaved in the cloth, and it is not known which it is, Rabbi Meir states, according to his reasoning, that it (i.e., the entire cloth) should be burned, and the Sages state that it is neutralized in one and two-hundred , according to their reasoning as seen in the dispute of above (see Mishnah 1 of this chapter).