Tractate Terumot - Chapter 7 - Mishnah 6 תרומות פרק ז׳ משנה ו׳

If one of these [baskets] fell into hullin, it does not render it medumma (doubtful terumah), but the second is treated as terumah and subject to the law of hallah, the words of Rabbi Meir. Rabbi Yose exempts it. If the second falls elsewhere [into hullin] it does not render it medumma. If both of them fall into one place, they render it medumma according to [the proportion] of the smaller of the two.