1. The measurement of a tallit that is obligated in tzitzit is [the size of a garment] that covers in length and width the head and most of the body of a child who goes out by himself to the marketplace and doesn't need someone watching him. Rema: And then it is obligated in tzitzit, and this is precisely that an adult would sometimes wear it in a temporary fashion to go out in it to the marketplace (Beis Yosef in the name of Ben Chaviv and in the name of MHRY"A).