The starting point of the multiple-prediction effect best known as “Confabulation” (named after a version of it by Alan Shaxon) would seem to be “Mental Projection Extraordinary” in The Life and Mysteries of the Celebrated Dr. Q by Alexander (stage name of Claude Conlin), 1921, p. 93. Two methods are given. The first involves a carbon impression inside an envelope; the second uses pocket writing.
In 1938, Earl Rybolt published a related effect with a similar title, “Rybolt's Miracle Thought Projection”, which he claimed to have been performing for fifteen years, which would date it to 1923, two years after the Dr. Q book was published. Rybolt's method involved an off-stage assistant, who wrote down spectators' free choices, which were delivered onstage for a switch. See The Sphinx, Vol. 37 No. 6, Aug. 1938, p. 140.
Stewart James made a significant advance in method with his “Perfect Prediction” in The Sphinx, Vol. 28 No. 4, June 1929, p. 140, which utilized double writing and loading of the prediction into a sealed envelope or nest of envelopes, using the load tube from the old “Ball of Wool” trick.
Shortly after this James item appeared, Theodore Annemann published “A Prophecy of the Koran” in The Book without a Name, 1931, p. 58. His approach involves a switch of the card sealed inside an envelope.
Tom Sellers was the next to submit a routine and method for the premise: “Prediction Extraordinary” in The Sphinx, Vol. 34 No. 8, Oct. 1935, p. 209.
Stewart James returned to the trick, essentially repeating his method from The Sphinx, in an article, “Two Fearless Feats” (the first trick of which was later retitled “The Ball of Fortune”), in The Jinx, No. 98, June 1940, p. 601. His method is the same, but the prediction is loaded into a ball of wool instead of an envelope, returning the loading tube to its original home.
Though he cites no precedents, William S. Houghton embellished on Annemann's structure and applied some of James's thinking in “'Prediction Supreme' Routine,” in The Magic 36, 1943, p. 21. Double writing is added to Annemann's card-in-envelope switch.
George Grimmond came up with “Triple Forecast” c. 1947. It was released in early 1951 by Harry Stanley’s Unique Magic Studio (see The Gen, Vol. 11 No. 6, Mar. 1951, p. 345). In Grimmond's trick, the prediction is found inside two nested envelopes that hang from a stand at the outset.
In 1948, Al Koran changed the container for his triple prediction to a wallet and contributed his routine to Pentagram, Vol. 3 No. 1, Oct. 1948, p. 1, where it appeared under the title of “A Letter from Al Koran”. By 1950 he had developed a “Dream Holiday” presentation for his performances of the trick. And by 1956 he was using a 'Dream Car“ presentation.
Specifically inspired by Grimmond's “Triple Forecast”, Alan Shaxon developed “Confabulation” in the 1960s, and later marketed it through Ken Brooke in 1970.
(This history courtesy of Max Maven, with an added citation by Yaniv Deautsch.)