Emma could not help laughing as she answered, "Upon my word, I believe you know her quite as well as I do. But, Mr. Knightley, are you perfectly sure that she has absolutely and downright accepted him. I could suppose she might in time, but can she already? Did not you misunderstand him? You were both talking of other things; of business, shows of cattle, or new drills; and might not you, in the confusion of so many subjects, mistake him? It was not Harriet's hand that he was certain of -- it was the dimensions of some famous ox." (Chapter 54)

It was me—I have linked my other post. It is funny to me. I think it means Harriet is not Emma's cow anymore but instead Mr. Martin’s:

Ox: The general name for black cattle; a castrated bull.