Ashtangasamgraha 27.25

27.25

pittāvasānaṃ vamanaṃ virekādarddhaṃ kaphāntaṃ ca virekamāhuḥ |

dvitrān saviṭkānapanīya vegān meyaṃ vireke vamane tu pītam ||

iti

susūkṣmaṃ kaphavātābhyāṃ vidyāddāraṇakaṃ tu tat ||

They say that emesis ends with pitta, and purgation is half that of purgation ending with kapha.
Having removed two or three urges accompanied by stool, the measure is taken in purgation, but in emesis, what was drunk [is subtracted].
So it is said.

Very subtle, caused by kapha and vāta: one should know that as dāraṇaka.