Sri Yukteswar Giri is the monastic name of Priya Nath Karar, an Indian monk and yogi, and the guru of Paramahansa Yogananda and Swami Satyananda Giri. Born in Serampore, West Bengal, Sri Yukteswar was a Kriya yogi, a Jyotisha (Vedic astrologer), a scholar of the Bhagavad Gita and the Upanishads, an educator, author, and astronomer. He was a disciple of Lahiri Mahasaya and a member of the Giri branch of the Swami order. As a guru, he had two ashrams, one in Serampore and another in Puri, Odisha, between which he alternated his residence throughout the year as he trained disciples. As a guru, he was nonetheless known for his candid insight, stern nature and strict disciplinary training methods, as noted by his disciple Yogananda in his autobiography.
Sri Yukteswar was born Priya Nath Karar in Serampore, India to Kshetranath and Kadambini Karar. Priya Nath lost his father at a young age, and took on much of the responsibility for managing his family's land holdings. A bright student, he passed the entrance exams and enrolled in Srirampur Christian Missionary College, where he developed an interest in the Bible. This interest would later express itself in his book, The Holy Science, which discusses the unity behind the scientific principles underlying Yoga and the Bible. He also attended Calcutta Medical College (then affiliated with the University of Calcutta) for almost two years.
He eventually was formally initiated into the monastic Swami order as "Sri Yuktesvar Giri" (note: thus 'Sri' is not a separate honorific, but part of his given name). "...many follow the usual procedure (for writing or saying someone's name informally) and drop the "Sri" and say only "Yukteswar", but this is not correct. If one wants to put a "Sri" at the beginning as in the prevalent fashion, then his name would look as: "Sri Sriyukteswar Giri."
In 1884, Priya Nath met Lahiri Mahasaya, who became his Guru and initiated him into the path of Kriya Yoga. Sri Yukteswar spent a great deal of time in the next several years in the company of his guru, often visiting Lahiri Mahasaya in Benares. In 1894, while attending the Kumbha Mela in Allahabad, he met the Guru of Lahiri Mahasaya, Mahavatar Babaji, who asked Sri Yukteswar to write a book comparing Hindu scriptures and the Christian bible. Mahavatar Babaji also bestowed on Sri Yukteswar the title of 'Swami' at that meeting. Sri Yukteswar completed the requested book in 1894, naming it Kaivalya Darsanam, or The Holy Science:
"The purpose of this book is to show as clearly as possible that there is an essential unity in all religions; that there is no difference in the truths inculcated by the various faiths; that there is but one method by which the world, both external and internal, has evolved; and that there is but one Goal admitted by all scriptures"
— Sri Yukteswar Giri
The work introduced many ideas that were revolutionary for the time[citation needed] – for instance Sri Yukteswar broke from Hindu tradition in stating that the earth is not in the age of Kali Yuga, but has advanced to Dvapara Yuga. His proof was based on a new perspective of the precession of the equinoxes. He also introduced the idea that the sun takes a 'star for its dual', and revolves around it in a period of 24,000 years, which accounts for the precession of the equinox.