Cosmological Lectures (1934 - 1940) - a definitive edition to provide a permanent record of the original text. The texts that follow are taken from the manuscripts P.D. Ouspensky used when he was lecturing. They are now in the library of Yale University in the United States of America (111 pages).
Pyotr Demianovich Ouspenskii (known in English as Peter D. Ouspensky, Пётр Демья́нович Успе́нский; was a Russian mathematician and esotericist known for his expositions of the early work of the Greek-Armenian teacher of esoteric doctrine George Gurdjieff, whom he met in Moscow in 1915. He was associated with the ideas and practices originating with Gurdjieff from then on. He shared the (Gurdjieff) "system" for 25 years in England and the United States, having separated from Gurdjieff in 1924 personally, for reasons he explains in the last chapter of his book In Search of the Miraculous.
All in all, Ouspensky studied the Gurdjieff system directly under Gurdjieff's own supervision for a period of ten years, from 1915 to 1924. His book In Search of the Miraculous is a recounting of what he learned from Gurdjieff during those years. While lecturing in London in 1924, he announced that he would continue independently the way he had begun in 1921. Some, including his close pupil Rodney Collin, say that he finally gave up the system in 1947, just before his death, but his own recorded words on the subject ("A Record of Meetings", published posthumously) do not clearly endorse this judgement, nor does Ouspensky's emphasis on "you must make a new beginning" after confessing "I've left the system".
The books contains some very interesting ideas that many would likely consider nonsense. This is not my perspective however, much of the ideas are too advanced for me to grasp from just one read. The law of octaves and all the information about hydrogens was quite confusing to me on first read. I do believe that there could be some validity to much if not all of the book though, assuming one is open minded enough to consider the alternative perspectives it offers.