In his 1886 book The Present Age and Inner Life, “Poughkeepsie Seer” Andrew Jackson Davis gives a surprisingly concrete explanation of table-turning at a seance:
We are negative to our guardian spirits; they are positive to us; and the whole mystery is illustrated by the workings of the common magnetic telegraph. The principles involved are identical. The spirits (improperly so called) sustaining a positive relation to us, are enabled through mediums, as electric conductors, to attract and move articles of furniture, vibrate the wires of a musical instrument, and, by discharging, through the potencies of their wills, currents of magnetism, they can and do produce rappings, on principles strictly analogous to the magnetic telegraph, and may move tables or tip them, to signify certain letters of the alphabet.
In her 1972 study of the spiritualist movement, Georgess McHargue writes that Davis’ scientific passages are so packed with “gobbledegook as to put it in the class with the most imaginative vintage science fantasy.”