Manava Dharmashastra 2.204

2.204

go'śvoṣṭrayānaprāsādaprastareṣu kaṭeṣu ca
āsīta guruṇā sārdhaṃ śilāphalakanauṣu ca //

He may sit with his teacher in a carriage drawn by oxen, horses, or camels, on a terrace, on a bed of grass or leaves, on a mat, on a rock, on a wooden bench, or in a boat.