“Those who want to practice laya yoga should also do some hatha yoga first. This is very important.
I do not mean asanas and pranayamas, because hatha never means those.
Classically hatha yoga has nothing to do with asanas and pranayamas, but it consists of a series of cleansing techniques* to bring about a balance between the sympathetic and parasympathetic nervous systems.
Asanas and pranayamas form a part of tantra.
Unfortunately, the modern yoga scholar and yoga scholars in the last century gave rise to this mistake because they thought it better if they said they were practicing yoga. I am sure that no yoga teacher in France has the courage to say: “I am teaching tantra;” instead he says, “I am teaching yoga”.
But let me emphasize again, he is not teaching yoga but is teaching only tantra, and asanas and pranayama form a most central part of the tantric system.”
* “... hatha yoga consists of six systems: neti, basti, kapalbhati, dhauti, trataka and nauli."
- Swami Satyananda Saraswati (from the book 'Insights Into Pranayama', p.66)