Gheranda Samhita is another text which describes Asanas and Mudras in details. Along with Hatha Yoga Pradipika and Shiva Samhita, it is one the 3 classic treatises on Yoga.
The performance of Asanas is done in order to gain Dhrirata or firmness.
So, Asanas, Mudras etc are practiced as part of a larger Yogic procedure.
The 2nd Chapter of this ...
The tag you added is for Yoga-Asana. But your question seems to be about seats.
I am answering for both.
Manufactured seats, like those made of wool, Kusha etc, are needed.
Seats made of wool, blanket etc are good to use. On the other hand, seats made of wood etc should be abandoned.
VamshAshmadharanidArutrinapallavanirmitam | ...
Yes apart from Hatha Yoga Pradipika a text called The Yoga Yajnavalkya is describing these asanas. Yoga Yajnavalkya is a dialog between well known Rishi Yajnavalkya and Gargi a Brahmavadini.
Chapter three of Yoga Yajnavalkya is describing list of eight asanas in detail with procedure. These Asanas are Svastikasana , Gomukhasana , Padmasana , ...
It is not recommended that you meditate while lying down. One has to sit at least in an upright position.
Quoting from the book "Meditation and its Practice" by Swami Rama.
Suggestions for Making Sitting Positions More Comfortable:
It is not recommended that you meditate while lying down. There are several reasons for this. One of the most important ...
Asana Siddhi in other words Mastery or achieving perfection in initial posture or sitting position before starting of meditation. Now there are many Asanas like lotus posture , Sukha posture in yoga system. But this term Asana Siddhi is not particularly associated with those types asanas we know , but related to basic sitting posture before starting of ...