Tosefta for Bava Batra 156:4

אדרבה אימא רישא אבל לא מכר לא את העבדים ולא את האנתיקי ואמרינן מאי אנתיקי אמר רב פפא עיסקא דבגוה ומדרישא בעודן עליו סיפא נמי בעודן עליו אלא תנא מילי מילי קתני

Now, since the first part [deals with the case] when it [the merchandise] is in it [the ship], the latter part<span class="x" onmousemove="('comment',' The Mishnah, supra 78a. ');">⁹</span> also [must deal with a similar case, which is] when it [the equipment] is upon it [the ass]!<span class="x" onmousemove="('comment',' But this assumption is in direct contradiction to the previous assumption; which is impossible! ');">¹⁰</span> But [the only way out of the difficulty is to conclude that] the Tanna dealt with different cases in the different parts of the Mishnah.<span class="x" onmousemove="('comment',' [H], 'words, words'. ');">¹¹</span>

Tosefta Demai