Tosefta על כתובות 51:12

Rabbi Shimon ben Gamliel says, "Just as the the presumptive status for the priesthood [is established by] the distribution of Terumah on the threshing floors (following Ketubot 25b:2, Steinsaltz tr.), so too, is the presumptive status for the Levites [established by] the distribution of the first tithe on the threshing floors. [However,] the distribution in the court does not [establish] for him the presumption of the priesthood (Ketubot 26a:7).