Sorry Marley23, I should have typed “the vessel with the pestle” as you correctly pointed out.
There were two drinks you see, that they were going to drink before the big duel. Having no legitamite chance of winning without incapaciting his much larger and more skilled opponent, Danny Kaye must put the “knock out drug” of choice in medieval times into his opponents drink. The two large cups (or perhaps mugs would be more accurate) had decorative symbols etched onto the outside of the glasses. One had a dragon, and one had a pestle (and I believe a third had something else before it broke and a new verse had to be quickly learned).
Now that I think about it, I believe the first mug broke because the opponent knew about this chicanery, and the scene before the fight started cut back and forth between Danny Kaye and his opponent, both repeating (to themselves) over and over the mnemonic verses in order to remember which was the right mug to grab.