Tosefta к Пеа́ 6:3

[If a farmer] took a sheaf in order to take it to the city, and [then] he put [this sheaf] down [on the ground] on top of his friend (i.e. another sheaf) [while still in the field] and [then] he forgot both of them [in the field where he put them down], then the bottom [sheaf] is [considered to be] Shikcha (forgotten sheaf), and the top [sheaf] is not [considered to be] Shikcha. Rebbi Shimon says, “Both of them are not [considered to be] Shikcha. The bottom [sheaf is not considered to be Shikcha], because it is covered [by the top sheaf], and the top [sheaf is not considered to be Shikcha], because [the farmer] acquired it [for himself].”

[If a farmer] stooked [some] sheaves in a field in which sheaves have been [laid out in a] mixed [fashion], and forgot one [of the sheaves, then this sheaf] is not [considered to be] Shikcha (forgotten sheaves), until he stooks all of the [other sheaves] around it.

What is [the case mentioned in the Mishna titled as] “a sheaf that is in front of it proves [that it is not considered to be Shikcha”]? Someone who had 10 rows [of sheaves with] 10 sheaves in each row, and he stooked one of [the rows in the direction] from North to South, and [then] forgot [the last sheaf in that row.] It is not [considered to be] Shikcha (forgotten sheaf), because [that sheaf] can be counted [as a part of the last row that goes] from East to West.