Tosefta על עבודה זרה 2:3

These are the “hides pierced at the heart” [which are mentioned in m. Avodah Zarah 2:3]: All that are perforated at its heart and made like a kind of aperture [in the roof looking to the ground floor]. But if it is straight, it is permitted. Preserved and boiled produce of idolators, into which it is customary to put wine and vineyard and Hadrianic earthenware, [they are subject to] a prohibition on benefit according to Rabbi Meir but the Sages say they are not subject to a prohibition on benefit. Pressed olives that are sold at the entrances to bathhouses are prohibited for eating and permitted for benefit. Rabbi Yosei prohibits them even for benefit because they pour vinegar on them in order to remove their pits.