[IMPENETRABLE SECRET] GROUP OF FOUR “MIND READING” PROPS AND PUBLICATIONS. Including: A Key of “The Japanese Parlor Magic.” Home Amusement to All. [Japan], ca. 1890s. Import[ed] by Andrew Kan & Co., China and Japan Fancy Goods, Portland, Oregon. Color woodblock printed wrappers and illustrations, stitched. — Aspinall’s Cards for Amusement, Instruction, and Social Pastime. Six cards printed in purple with common phrases and sayings, plus a key card, instruction sheet, and printed envelope. Middlesbrough: Burnett and Hood, ca. 1870s. — BIRCH, E. Le Nouveau Secret Impenetrable: or, Geographical Recreations. London: Printed for the Author, by H. Barnett, and by Mr. J. Harris, n.d., [ca. 1810s?]. Marbled case containing a two-page instruction sheet, and two sets of a dozen loose 8vo sheets (one set numbered with Arabic numerals, the second with Roman numerals). — Das Gedankenspiel oder die kunst der Menschen Gedanken zu erforschen. Halle: J.C. Hendel, ca. 1782.
These sets, all based on the same early principle, allow the magician to instantly divine what image, phrase, number, or term the reader has thought of. The trick was the first one advertised in America, when Benjamin Franklin in 1749 wrote in the Pennsylvania Gazette, “Just published and to be sold at the Post-Office, the Impenetrable Secret.” The trick was an old one then, and its origin remains uncertain.