Some of these obstructions may be counteracted by yogic meditation or by sitting postures, practiced together with concentration, and others may be counteracted by special austerities, mantras or medicinal herbs. By meditating on the moon and sun, heat and cold can be counteracted. By āsanas, along with meditation on air, one can counteract sickness arising from vāta. By austerities, mantras and medicines one can counteract troubles caused by bad planets or snakes etc.