Siman 271

In siman 197, the laws of kinyanim for animals were explained, and it was explained there in section 6 that regarding riding alone there is a dispute among the poskim whether one acquires in a sale, but regarding ownerless property and a find, according to all opinions riding alone is a kinyan [Beit Yosef there, and the difficulty of the Sma subsection 5 is settled]. And if two were riding, both of them acquire, and we do not say that one is primary and the second is secondary. Our teacher, the Beit Yosef, wrote there that even according to the one who holds that one acquires by riding alone and we do not require leading with the feet, nevertheless, riding while it stands in its place is not a kinyan, and we require that it move slightly so that a hand and foot are uprooted. Furthermore, it was explained there that leading is a kinyan like meshikhah, and even if he led it with a voice or struck it with his staff and it ran before him, it is a kinyan. Therefore, if both were leading, or one was riding and one was leading, both of them acquire and shall divide. And so too if one pulls and one leads. And the opinion of the Rambam in chapter 17 of Avidah is that regarding a camel, even though each one individually would acquire, nevertheless, if one was pulling and one was leading, the kinyan of meshikhah nullifies the kinyan of leading, for regarding a camel the kinyan of meshikhah is superior as its way is not so much by leading.

This is the wording of the Rambam and the Shulchan Aruch: Two who saw a camel or a donkey of a find, and both of them preceded and led it or pulled it, or one was leading and one was pulling, both of them have acquired it. In what case does this apply? Regarding a donkey. But regarding a camel, if one was leading and one was pulling, the one who pulls has acquired it, but not the one who leads. Thus far his words. [For it is explained in Bava Metzia 9a: There is one side that does not acquire, meaning in the place of another acquisition, and he ruled according to the "some say" as is its way]:

We further explained there that some of the poskim hold that a camel is acquired only through meshikhah and a donkey only through hanhagah, but conversely, there is one among them for which it is not an acquisition. Since there is a doubt, it follows that a camel is not acquired through hanhagah nor a donkey through meshikhah. However, this is only regarding sale and gift, but regarding a found object and ownerless property, one acquires both through both methods of acquisition, and we do not remove it from the hand of the one in possession [the Rosh there]. In sale and gift, establish the money in the possession of the first owner [the Tur there]. And if two performed an acquisition on an ownerless donkey or a found object, this one through meshikhah and this one through hanhagah, and afterwards the one who performed hanhagah seized it and says, "My acquisition was certainly an acquisition and yours is a doubt, and since I am in possession I will not give you a portion," it appears to me that he can say so according to these poskim, and similarly conversely regarding a camel. However, our teachers, the authors of the Shulchan Arukh, hold like the Rambam and omitted this law there.

We have further explained there in section 2 that there is a kinyan of mesirah regarding a sale, but regarding a find or ownerless property, this kinyan is not applicable, for who is there to hand it over to him? Therefore, regarding an animal that is a find, where one preceded others and seized it by its mosirah—which is the bridle or the rope hanging from its neck, with which one hands over an animal from hand to hand—he has not acquired it until he pulls it or leads it. And so it was with the property of a proselyte in ancient times. However, he has acquired the mosirah alone, specifically the portion held in his hand [Shach and Taz]. If one was riding and another was holding the mosirah, the rider has acquired the animal and only the part of the mosirah that is on the animal's cheeks, for this part is nullified to the animal. And this one who held the mosirah has acquired of it what he held in his hand, and the rest of the mosirah was acquired by neither this one nor that one. And if a third party comes and seizes it, it is his, and his seizure does not benefit the rider like one who lifts a find for his fellow in siman 269, for here he lifted it for his own sake; and since he did not acquire it, how shall the rider acquire it [Gemara ibid.]?

The finding of documents and receipts was explained in siman 65, and the finding of a get in Even HaEzer siman 132 and siman 153.