Aparihaniyasutta 5.4

5.4

rattiyā majjhimaṃ yāmaṃ dakkhiṇena passena sīhaseyyaṃ kappeti, pāde pādaṃ accādhāya, sato sampajāno uṭṭhānasaññaṃ manasi karitvā;

In the middle watch, they lie down in the lion’s posture—on the right side, placing one foot on top of the other—mindful and aware, and focused on the time of getting up.