What has become known as "Kundalini yoga" in the 20th century, after a technical term particular to this tradition, is actually a synthesis of many traditions which, according to Gaia, "is a blend of Bhakti Yoga (the yogic practice of devotion and chanting), Raja Yoga (the practice of mediation/mental and physical control) and Shakti Yoga, (for the expression of power and energy). " However, it may include haṭha yoga techniques (such as bandha, pranayama, and asana), Patañjali's kriya yoga (consisting of self-discipline, self-study, and devotion to God), tantric visualization and meditation techniques of laya yoga (known as samsketas), and other techniques oriented towards the 'awakening of kundalini'. Laya may refer both to techniques of yoga, and (like Raja Yoga) its effect of "absorption" of the individual into the cosmic. Laya Yoga, from the Sanskrit term laya meaning "dissolution", "extinction", or "absorption", is almost always described in the context of other Yogas such as in the Yoga-Tattva-Upanishad, the Varaha Upanishad, the Goraksha Paddhati, the Amaraugha-Prabodha, and the Yoga-Shastra of Dattatreya. The exact distinctions between traditional yoga schools is often hazy due to a long history of syncretism, hence many of the oldest sources on Kundalini come through manuals of the tantric and haṭha traditions such as the Hatha Yoga Pradipika and the Shiva Samhita. The Shiva Samhita describes the qualified yogi as practicing 'the four yogas' to achieve kundalini awakening while lesser students may resort solely to one technique or another: "Mantra Yoga and Hatha Yoga. Laya Yoga is the third. The fourth is Raja Yoga. It is free from duality. "