Here is another example, well attested, even if it went unnoted until recently, and which, if not of the same kind, nonetheless has something very harsh about it. Among these same Romans, up until the time of Praetor Cajus Aquilius Gallus, in other words for more than three centuries following the establishment of the laws of the Twelve Tables, one had to take every care not to use-even in jest-the consecrated terms of stipulations or formal promises. Suppose one father had said to another, in conversation or at a festival, when nothing was further from the issue than discussion of serious business: "Do you want to marry your daughter with my son?," if the other person had responded, by way of joking and banter: "I so wish," then the former had only to take him at his actual word. The party for his son was found. It was futile for the girl's father to claim that he had neither intended nor given reason to believe that he had any such marriage in view; it was futile for him to prove that the words by which he had supposedly committed himself meant nothing more, in the circumstances in which they were uttered, than if he'd spoken them in his sleep. No joking was tolerated, and the judge would without further trial find against him. It was obligatory to go through with what an impertinent plaintiff wanted, one who under the pretext of an apparent agreement, extorted an imaginary promise as unjustly and with all the violence of a highway robber. Such was, for some centuries, the superstitious attachment of the Roman courts to the letter of the law and its formulas, and this despite a manifest intention to allow these words a usage quite other than that which they had at law. Even when the Praetor, of whom I spoke, had recognized the injustice and the need for a remedy, he dared not act directly; he contented himself with avoiding the plea by allowing an exemption from fraud for the party whom the other was bold enough to summons to fulfill a promise that had not in fact been made.

(http://www.autoadmit.com/thread.php?thread_id=5821363&forum_id=2.#49585168)