Manava Dharmashastra 6.22

6.22

bhūmau viparivarteta tiṣṭhed vā prapadair dinam
sthānāsanābhyāṃ viharet savaneṣūpayann apaḥ //

Let him either roll about on the ground, or stand during the day on tiptoe, (or) let him alternately stand and sit down; going at the Savanas (at sunrise, at midday, and at sunset) to water in the forest (in order to bathe).