Lay out twenty cards of any kind, two by two, and request a friend to think of two in a line; that is, one of the ten sets formed by the twenty cards. This done you take up the sets in the order in which they lie, and place them in rows according to the letters of the following words:—

You may use a diagram like the above, but as the words are easily retained it had better be dispensed with, distributing the cards on the table just as though upon the diagram, which will make the trick more puzzling and extraordinary. Proceed as follows:—Place the cards two by two on similar letters: thus, place the two cards of the first set on the two d’s in dedit; the two cards of the second set on the two i’s of cicos and dedit; the two of the third set on the two c’s, and so on with the ten sets.

All the letters of the words being thus covered, ask the friend who has thought of the cards to tell you in which lines these cards are. If both are in the first line (cicos), they must be those on the two c’s; if they are both in the second line, they cover the d’s in dedit; both in the third line, they cover the u’s in tumus; both in the fourth, they cover the n’s in nemon.

If one be in the first line and the other in the second, they cover the i’s in cicos and dedit, and thus of the rest—the two cards thought of necessarily covering two similar letters, whilst each of the letters occurs only twice in the diagram.

Excerpt from the book: Three Hundred Things A Bright Boy Can Do