(Mishnah): There are four laws pertaining to sellers...

If he sold him good quality wheat and it turned out to be bad quality, the buyer can back out.

If he sold him bad quality and it turned out to be good quality, the seller can back out.

If he sold him bad quality and it turned out to be bad quality or he sold him good quality and it turned out to be good quality, neither can back out.

If he sold him dark wheat and it turned out to be white; or white and it turned out to be dark; if he sold him olive wood and it turned out to be sycamore wood; or sycamore wood and it turned out to be olive wood; or if he sold him wine and it turned out to be vinegar or vinegar and it turned out to be wine; both can back out.

If a person sold produce to his friend, if he took them but did not measure them out, he acquires them. If he measured but did not take them, he does not acquire them.

If he is astute, he will hire the property underneath them.

If a person bought flax, he only acquires it when he takes it from place to place.

If it was still attached to the ground, as soon as he detaches a small amount, he acquires all of it.

If a person sells wine or oil and they increased or decreased in price; if it occurred before it was measured out, the gain or loss goes to the seller. If it was after measuring out, the gain or loss goes to the buyer.

If there was a middleman; if the barrel broke, it is the middleman's loss.

He must give him three additional drops (after pouring the wine or oil).

If after this, he tilted the bottle and some more drops accumulated, they belong to the seller.

A shopkeeper does not need to give the additional three drops.

R. Yehudah: He also does not need to give them just before Shabbos.

(Gemara) - question: (The Mishnah said that if the price change occurred before measuring out, the gain/loss goes to the seller; if it was after, it goes to the buyer.) Whose measuring vessel is it?

Answer: If the vessel was the seller's, the seller can back out. If it was the buyer's, the buyer can back out.

R. Yehudah citing Shmuel/ R. Ila citing R. Yehudah b'Rebbi: The Mishnah could be referring to another person's vessel. (Therefore, the one who suffered the gain/loss depends on whether or not it was already measured out.