In Lord of the World, the French esotericist Rene Guenon comments on the presentation in Parzival  of the Grail as a green stone rather than a chalice. “This emerald strongly recalls the “urna” or Hindu frontal jewel (subsequently adopted by Buddhists). It usually depicts the place of the third eye of Shiva, representing what can be called the “sense of eternity”.

The astonishing autobiography of the modern Indian adept Swami Muktananda, Play of Consciousness, describes a yogic kundalini process leading to a supreme attainment known as the vision of the blue pearl, symbol of the supreme self, of Shiva. It does seem to parallel many elements of the Grail literature.

Innumerable examples throughout the medieval romances tell of assorted ecstasies in terms that seem descriptive of physiological processes. When the eastern mystics talk of enlightenment they know that the yogic mystic techniques can induce experiences of overwhelming light, the most often reported sign of the presence of the Grail. This light may be felt as permeating the whole body-mind, producing swooning trances of love bliss. The terminology of the time would speak of the recipient being filled with the Holy Spirit. The Grail seems to be infinitely nourishing. Some are fed what they most desire until they lose all need of food. It heals wounds and prolongs life. 

On the path to such fulfilments there may be problems. The accounts of knights who are blinded, lose the use of their limbs, or are burnt to a cinder when approaching the Grail in an unprepared and unworthy state, may be indications of what the eastern adepts would recognise as signs of a prematurely or wrongly awakened kundalini. In Malory, Lancelot sees the blinding Grail light and hears a voice warning him to go no further. He carries on regardless and is hit in the face by a fire, collapsing and losing all control of his limbs. Some around him think he has died but an old man comments that he, “has more life in him than the strongest among you.” Lancelot remains in an apparently catatonic state for twenty four days, eventually awakening to tell of the bliss he has experienced.