More nonsense. Russell's date system was derived from Anglican writers, especially E. B. Elliot's Horae. Russell saw substantiation of his beliefs in the Pyramid but saw it as a poor basis on which to base one's faith. In 1881 Russell addressed widely spread expectations concerning 1881 saying that his belief did not rely on pyramid measurements: "Now to us, these things seem a poor and weak foundation for the hopes built upon them. Our belief that the Lord is present, is based on the “more sure word of prophecy” to which Peter said, we would do well to take heed." [C. T. Russell: The Year 1881, Zion’s Watch Tower, May 1881, page 5.]
Pyramidology was current in his day and many well-known Protestant clergy believed similarly. This included Seiss, a Lutheran whose works are still reprinted as classics of Christian exposition, and C. Larkin, a Baptist whose works are still admired. H. J. Lambert, once a prominent Australian Baptist clergyman, told the Hill Street Baptist Church that the Great Pyramid pointed unmistakably to 1881; it wouldn’t mark the end of the world, but a “great change would take place in that year.” [Church Anniversary – Lecture on the Great Pyramid, The Kapunda, South Australia, Herald¸ May 23, 1879.] In 1877 the Advent Christian Church [Not SDA] published a booklet advocating similar views.
Schulz: Separate Identity, vol 2 observes:
"In volume one, we asserted considerable interest in the Great Pyramid as a prophetic witness to “God’s Plan.” Interest reached its peak as 1881 approached with lectures and booklets proliferating. A detailed history of pyramidology is inappropriate here. A few examples will do. James French, a Baptist clergyman, presented two lectures on the pyramid’s significance to the Baptist Ministers’ Conference. The first lecture, delivered in New York City. Baptist clergy listened attentively for an hour and a quarter, thanking him and arranging for part two. French turned his lecture into a series of articles for Baptist Family Magazine.
"French was far from unique. Dr. Rufus W. Clark, a Reformed clergyman, also advocated pyramidology. J. A. Seiss lectured with some regularity through 1883. Edson Rogers, a Congregational clergyman from Cincinnatus, New York, did as well. Newspapers of the period note numerous lectures on the topic by clergymen, self-appointed and real professors and “experts,” all of whom saw the pyramid as a prophetic witness and many of whom pointed to 1881 as a year of destiny. Watch Tower and Barbourite belief may seem strange from our vantage point, but compared with contemporary belief, it was tame.
"As late as August 1881, S. A Chaplin, editor of The Restitution, suggested that “the Great Pyramid indicates some great political event in 1881-2. A great change in human affairs is impending and at the door.” Barbour gave his readers a summary of Charles Piazzi Smyth’s pyramid measurements, concluding that this was “an interesting coincidence ... as the floor measure points to 1881, for, as we believe, the commencement of the return of literal Israel; the 6 years, ‘impending,’ is the exact measure of the time from the spring of 1875, where according to the jubilee cycles, the ‘times of restitution,’ should have begun. Again: The mouth of the well, the type of Christ's death, is 33 inches from the Grand Gallery; and this 33 inches added to the measure of the Grand Gallery floor 1881, make 1914, the date of the end of ‘The Times of the Gentiles.’”
Russell's view of the Pyramid had nothing to do with spiritism, but with the belief that Melchizedek built the pyramid to stand a a prophetic reference. In its day Pryamidology attracted many clergy. Russell followed the crowd, persuaded by the coincidence that some measurements matched the chronology he adopted from Elliot and a host of other clergy, primarily Anglicans and Presbyterians.