Bava Batra 54 - Acquiring Land by Lying Down on It
Said Rav Amram, "The following ruling was told to us by Rav Sheshet, and he enlightened our eyes by adducing a proof to it."
A convert is like a new-born child : he has severed connection with his old family, and if he has not created a new one yet, he has no inheritors. One who spreads out mats on the ownerless land of a deceased convert and lies down upon them has acquired the land.
One can acquire a Canaanite slave by means of a propriety act, such as having the slave put on a shoe for him, remove his shoe, or lift him. We see that supporting the weight is a propriety act - and so it is with land: spreading the mats and lying down on it constitutes a proprietary act. Compare this to a slave woman.