Tosefta for Bikkurim 2:4

These are the things that have no set amount: the peah, the bikkurim, the r'iyah, charity, and learning Torah. Peah has a minimum amount but does not have a maximum amount. [If] one makes his entire field peah, it is not peah.

Rebbi Yehuda says, “A person who made his whole field into sheaves [in order to later] stook them [into stooks, which in turn will be taken to the final stack] is [considered to be] like someone who bundles [sheaves] in [order to put them in a] stack [of sheaves, which makes the sheaves inside the stooks eligible to become Shikcha (forgotten sheaves),] and [then] rounded it (i.e. the stack) out [as if he has completed the stack] and [then brought more sheaves and] pressed [them] into the stack [after the stack seemed to be already finished, which is still considered to be the final act of bundling, which makes these sheaves eligible to become Shikcha].” Bet Shammai and Bet Hillel agree that if [a person] proclaimed [his produce to be] ownerless [only] to people, but not to animals, [or only] to Jews, but not to Non-Jews, [it is still considered to be] ownerless [and anyone can come and take it].