Ashtangasamgraha 26.9

26.9

pūrvavat svedadravyāṇi kumbhyāmutkvāthyāśliṣyopaviṣṭastadvadūṣmāṇaṃ gṛhṇīyāt |

bhūmau vā tāṃ nikhāya tadūrdhvamāsanaṃ śayanaṃ vā nātighanapracchadaṃ paritaḥ pralambamānakuthākambalagoṇikaṃ nidhāya tatrasthasyoṣmāṇaṃ gṛhṇataḥ kumbhyāmagnivarṇānayoguḍānupalāṃśca śanairnimajjayediti kumbhīsvedaḥ ||

Having boiled the sudation substances in a jar as before, one should sit close to it and take in the vapor in that manner. / Or, having buried that [jar] in the ground, placing above it a seat or a bed with a cover that is not too thick and with blankets, woolen rugs, and hemp covers hanging down all around, while the person stationed there takes in the vapor, one should gently plunge fire-glowing iron balls and stones into the jar; this is jar sudation.