I saw a video a little while ago of Ven yuttadhammo in which he tells a story of a monk who is dozing and instead of contemplating rising and ceasing his mind is caught on a passing bird and he concentrates on the aspect of the bird which has a similar sound to whatever the Pali for rising ceasing. The Buddha sees this and remarks that the meaning and the designation are important. Does anyone have a source for this?
I could only find SN17.9, which has the gist of the lesson but not the wording:
Some take his robe, others his bowl, others his sitting cloth, others his needle case, just like the bird flung about by the gale-force winds