It so happened in India, that spiritual practices are most often performed facing east. Accordingly, the west (conditionally) is our back, the south is the right and hot side and the north is left and cold. The Sun is associated with vital power, it rises in the east and sets (i.e. disappears) in the west. We fall asleep at sunset and our senses become silent, and they turn on at sunrise. We can see basically everything that is in front of us, on the sides, below and even sometimes from above, but we cannot see our back. We can only feel it, while there should be an inversion element, i.e. direction inward, listening to our sensations inside. The west is a symbol of the extinction of activities, the completeness of them, so it is suṣumṇā. It is also no coincidence that one of the well-known traditions, where kuṇḍalinī is worshiped in the form of the Goddess Kubjikā, is called paśchimāmnayā – the Western Doctrine. Paśchima – from paścāt (behind, the last, completed, western), therefore it is a symbol of suṣumṇā, self-absorption. Thus, paścimottānāsana is focused specifically on the direction of attention and the prāṇa in suṣumṇā along with it. This āsana is also focused on the conscious activation of suṣumṇā with pratyāhāra and the awakening of the kuṇḍalinī power.
The idea of 84 āsanas, which is often found in yoga texts, is based on the worship of 84 nātha–yogis. Each of these 84 nāthas is responsible for the evolution of one lakh of living beings (100,000). When you follow the yoga path, you develop the psychophysical, spiritual purity in yourself, that you radiate into space. By doing your practice you help not only yourself, but also your close ones. Souls reincarnate in different forms until they become perfect yogis, the symbolism of 84 āsanas is based on this principle. The most important thing here is to understand that āsana is not just a physical process, but also a psychophysical one. The purpose of many āsanas is to be able to stay stable in the position of siddha (siddhāsana). Generally, it is the ability to stay in a meditative posture for three hours, to hold it easily, so that you can meditate, remaining in the position, on something sublime and pure in it.