Manava Dharmashastra 6.24

6.24

upasparśanaṃ snānam | anyadapi ūrdhvabāhādi māsopavāsadvādaśarātrādi tapaḥ | ugrataraṃ prakṛṣṭataraṃ śarīrapīḍājananaṃ kurvan śoṣayeccharīram |

Medhātithi’s commentary (manubhāṣya):
‘Upasparśana’—means bathing.

‘Austerities’— such as holding up the arms permanently, fasting during the whole month, or for twelve days, and so forth.

‘Harsher’—what is calculated to cause greater suffering to the body.

He shall ‘emaciate’,—make to dry up,—his body (24).