Commentary for Nazir 55:7

And it is taught - as a support to the idea that Rabbi Yosei does not declare him impure until he removes his head and the majority of his body. And that which Rabbi Yosei, son of Rabbi Yehuda, taught above, that if one threw a box full of utensils over a corpse, [the box and everything inside it] is impure -- is not because he holds that a moving tent is not called a tent. Rather, since he threw it, he removes it from the status of being a tent, and equates it with the status of being a utensil. Actually, he holds that a moving tent is called a tent, since it teaches in the latter clause that "if it was placed down, it is pure" -- even though it is normally carried [around].