“Sikhism and Tantric Yoga” is a rare and out of print book. I discovered the book during my two years in India. “Sikhism and Tantric Yoga” has been a real eye-opener for me and makes complete sense when I think about the last thirty years of my life with Yogi Bhajan. Written by the esteemed Dr. Trilochan Singh, author of over twenty books on Sikh history and philosophy and lecturer at sixteen Universities, “Sikhism and Tantric Yoga”, describes the Sikh mystical path and is critical of Yogi Bhajan's Tantra and Kundalini Yoga.

I have included here a sample of one chapter and the entire book can be downloaded at: “Sikhism and Tantric Yoga (e-book)." GurmukhYoga.com

What I learned in India about the Sikh Mystic Path

By Guru's grace, while being detained by authorities in India, I lived for almost one year at the Golden Temple. After visiting Guru Sahib at the Harmandir Sahib everyday, singing the divine Gurbani Kirtan and contemplating God's Name, the Guru showed me, how all the Yogic asanas I performed over the last 30 years were a complete waste of time and cannot match to 1 percent of the devotional contemplation on the Name of God.

“In contrast to Patanjali's Yoga, and other schools of Hindu Yoga (Hatha, Tantric, Laya, Kundalini, etc.), the Sikh Gurus call Sikh mystic path, Brahm Yoga (the Yoga which does not use any yogic technique but concentrates on God and achieves Him through devotion and contemplation). It is also called Gurmukh Yoga (Yoga of the Enlightened), Sahajya Yoga (Natural Yoga based on spontaneous devotion and contemplation). The word Yoga is used just to mean union with God.” Dr. Trilochan Singh.

II
Eight Steps of Sikh Mystical Path
…....Thus Guru Nanak clearly rejects the eight steps of spiritual progress as enunciated by Patanjali and replaces them with ethical and spiritual discipline of his own. The Sikh scriptures also clearly reject asanas (physical postures), pranayama (breath control), nauU-dhautz (cleaning the intestine with a piece of cloth inserted in the mouth and taken out through the anus). Those followers of Yogi Bhajan who frequently quote him as saying that the Scriptures of the Sikhs sanction all these Yoga practices, voice only his glaring ignorance of Sikh scriptures. I have not known any saint or seer in contemporary or past Sikh history who ever practiced these Yoga asanas. But all saints and all scholars have firmly called these and more so Tantric practices as directly opposed to Sikh doctrines. The following quotations, from Adi Granth make it clear that there is no place for Yoga practices in Sikhism:
If a man learns all yogic asanas of perfect adepts, If he controls and subdues his senses through such feats;
Even then impurity and dirt of his mind cannot be removed.
The filth of egoism will not depart from the heart. The human mind cannot be cleaned and made pure, By any yogic discipline and restraint. It can be made pure and controlled only by seeking, Through love the sanctuary of the true Enlightener.
Adi Granth, Guru Amar Das, Vadhans p 558
For me the only asana (posture) worthwhile is to fix steadfastly the mind on the Vision of God and let the heart and soul be absorbed in such a spiritual condition of transcendent revelation as to continuously reflect on His Presence and listen to the enchanting melody of Unstruck Music (Anhad Shabad)
(a) Savikalp Samadhi (ecstasy within the realm of consciousness): to be absorbed in the meaning and philosophical and mystical contents of the Divine Word is Savikalp a samadhi. (b) Nirvikalpa Samadhi (ecstasy of the Transcendent vision of God): to be absorbed in the Spirit and Essence of the Divine Word is Nirvikalpa samadhi.
If one does the nauli dhauti karma (of cleaning the intestine with a piece of cloth), and becomes adept in eighty-four asanas, and yogic exercises, he cannot attain any peace of mind by these yogic techniques. Let him do such Japa or Tapa through such techniques for years and years and wander about in search of perfection, he will not attain genuine inner peace even for a moment.
A. G. Guru Arjan, Majh, p 98
Let one practice nauli and dhauti and all the elaborate yogic feats associated with it; let one make an offering of incense and light lamps before the Deity. None of these yogic feats and formal acts of worship match with devotional contemplation of the Name of God.
A. G. Guru Arjan, Sarang, p 1229