and this is like land. However, the buyer has no right of rescission, while the seller is compelled to make up the deficiency. If it turns out to be more, such as where he says, “I sold you this heap of food as one hundred kilograms,” but it proves to be one hundred and twenty kilograms, then the sale is valid and the surplus belongs to the seller.
If the buyer says, “If he takes the surplus, then I have the right of rescission,” the commentator says: “He has no right of rescission.”
And if the seller says, “I have the option either to take the surplus or to rescind the sale,” we say: You have no option at all; the surplus belongs to you, so take it.
What, then, is the difference? We say: the difference is that land cannot be increased or diminished. That is, if he sells it as one hundred metres and it turns out to be ninety metres, he cannot bring an additional metre and add it to those ninety. But in the case of a heap of food, he can bring other food of the same kind and make up the deficiency; and the same applies when there is a surplus.
However, it should be said that if it turns out to exceed the stipulated amount, and the buyer has a particular purpose in the heap itself—for example, he had estimated that this heap would suffice for the guests he has—then, if the seller wishes to take the surplus, the remaining amount will not, in the buyer’s estimation, suffice for his guests.
We therefore say that his purpose has been frustrated, and he has the right of rescission. The implication of the previous principle is that whoever has had his purpose frustrated has the right of rescission, because the amount has fallen short—unless the seller says to the buyer, “I will make up the one hundred kilograms for you with food of the same kind.” In that case, the buyer has no right of rescission, because his purpose has not been frustrated. But if his purpose is deemed to have been frustrated because the seller delayed making up the amount, or brought food inferior to that which was the subject of the contract, then the buyer has the right of rescission.