Ramana Marahshi on asanas:
Questioner: But hatha yoga is so much spoken of as an aid.
Ramana’s Answer: Yes. Even great pandits well versed in the vedanta continue the practice of it. Otherwise their minds will not subside. So you may say it is useful for those who cannot otherwise still the mind.
Q: What are asanas [postures or seats]? Are they necessary?
A: Many asanas with their effects are mentioned in the yoga sastras. The seats are the tiger- skin, grass, etc. The postures are the ‘lotus posture’, the ‘easy posture’ and so on. Why all these only to know oneself? The truth is that from the Self the ego rises up, confuses itself with the body, mistakes the world to be real, and then, covered with egotistic conceit, it thinks wildly and looks for asanas [seats]. Such a person does not understand that he himself is the centre of all and thus forms the basis for all.
The asana [seat] is meant to make him sit firm. Where and how can he remain firm except in his own real state? This is the real asana.
Attaining the steadiness of not swerving from the knowledge that the base [asana] upon which the whole universe rests is only Self, which is the space of true knowledge, the illustrious ground, alone is the firm and motionless posture [asana] for excellent samadhi.
Q: In what asana is Bhagavan usually seated?
A: In what asana? In the asana of the Heart. Wherever it is pleasant, there is my asana. That is called sukhasana, the asana of happiness. That asana of the Heart is peaceful, and gives happiness. (The name comes from the Sanskrit words Sukha meaning “pleasure”, and Asana (आसन, Āsana) meaning “posture” or “seat” and also “foundation”.)
There is no need for any other asana for those who are seated in that one.
(excerpt from “Be As You Are – The Teachings of Sri Ramana Maharshi” by David Godman