This was a Tantric system that included knowledge of jyotisha (Vedic astrology), sacred rites and rituals and devotion to Shiva and the Shakti or goddess personified as power. It was a highly specialised system with many deeper elements to it, as in the greater Tantric path, not simply superficial or rudimentary occultism as it is often perceived today!
BKS Iyengar, the brother-in-law of Krishnamacharya later learnt this system of Hatha-Yoga under him and took it to the West. Iyengar made this system available to one and all, yet Krishnamacharya synthesised it more with Ayurveda at a deeper level and gave his patients personalised instruction.
This is an example of how a rajasic militant-Yoga system for Pitta-type kshatriyas (those of muscular, bilious phenotypes as warriors) has become reduced down to a “one-size fits all approach”. While Iyengar himself taught cautions, they have fallen on deaf ears of his followers who have turned it simply into a vyayama (exercise) cult.
While preaching Jnana or the path of knowledge, modern Iyengar yoga teachers also forget that Krishnamacharya and Iyengar belonged to the Sri Vaishnavas in Ramanuja’s lineage of Bhakti–Yoga, not the Advaita system commonly preached today of Shankaracharya’s Advaita system or Jnana–Yoga! They also forget the aggressive nature of the original Hatha-Yogis that didn’t take the Gandhian-styled ahimsa (non-violence applied to all situations) into account – the system was developed to generate warriors who protected India, dharma and yoga traditions – otherwise we’d not have them to use today and would be replaced by Islam as with all other traditions in the Middle-East, Afghanistan, Pakistan etc.