A kind of Pratisaṃlīnatā (a kind of external austerity);
practice of the austerity of Pratisaṃlīnatā by curbing the activities of the limbs (such as hands, legs etc.) of the body like a tortoise withdrawing its limbs (under its shield).
jaṇṇaṃ susamāhiyapānipāe kummo iva guttimdie savvagāyapadisamlīne citthai. se tam kāyajogapadisamlīnayā.
(Aupa 37)