Our body is restless and cannot be still for long. Asana practice helps us to gain restraint and control over the body so that it behaves as we want it. Hatha Yoga is aims to bring strength and flexibility to the body so that it can be stable without discomfort during Meditative practices. The best posture for Meditation is the Lotus posture known as Padmasana in Sanskrit.
The Surya Namaskar or Sun Salutation is devoted to the worship of the Sun. It is generally done at the beginning of any yoga Practice and acts as a great body warming flow. Suryanamaskar is a combined process of Yoga Asanas, Pranayama & Dhyana. When the focus is on the alignment of the body, it is flow of 12 Asanas.
The Vajra or thunderbolt is the weapon of Lord Indra, the King of the Gods. In Sanskrit the term 'Vajra' relates to firm, determined & decisive Awareness. In yogic context, Vajra refers to Vajra Nadi (Energy Channel), which governs the uro-genital system and is responsible for sexual behaviour. The control of the Vajra Nadi sublimates sensual energy and channelise it towards activating higher brain centres. All Yogic practices are aimed towards this.