This book unfolds the true essence and esotery of Yogiraj Shamachurn Lahiri Mahasaya, the Fountain-Head of Kriyayoga, the Greatest Household-Yogi with an impeccable stroke of dexterity by the author. Author has laid bare the essence, concept, philosophy, the Esse, the sublime spirituality and spiritual sublimity of Shamachurn for human comprehension. Through the purview of dharmaic history, philosophy, science, spirituality, yogasastra, mathematics, astrology and Sanatana Dharma, a profound exegesis on the Life and Ideals of Yogiraj Shamachurn Lahiree Mahasaya has been conferred in this book. For the first time such an introspective scientific rational expatiation on Shamachurn resulting in harmonious fusion of history, philosophy, religion, logic, science is done. This book unfolds the truth that Shamachurn is Indefinable, Unquestionable, Non-Answerable, Incomparable, Non-Debatable, Undefinable, Irrefutable, Indivisible. Shamachurn vis-a-vis Bhagavan Krishna, Bhagavan Rama, the four yugas, Babaji has been delineated with an intrinsic easefulness in this book. This book unravels the essence of Prana lucidly yet in a compelling manner and explains the abstruse esotery of Prana. The book is forceful yogic expose on Prana scientifically (yogic science) analyzing the Esse of Yogiraj Shyamacharan Lahiree- Absolute Prana, the Origin and Mergence, the Progenitor, the Primordial; everything within and beyond yet nothing, thus the Allness yet Nothingness. This is essentially a book for soul-seekers. It expounds the fact that spirituality transcends religion. Through this book the author has exposed the flagrant nudity of religion and spiritual culture being abided by today. At the end of the book in the Appendix both the Horoscopes of Bhagavan Krishna and Bhagavan Sri Shamachurn has been assessed. This book has mass appeal throughout India and abroad and has been translated and published in Hindi and English, original being Bengali.