Double and triple acrostics occupy an important niche in the history of word puzzles, it is generally recognized that they were the predecessors to the crossword puzzle. For those unfamiliar with the genre, a double acrostic consists of clues for a sequence of words (the cross-lights) to be written in a list, plus two clues to the words spelled out by the first and last letters of the cross-lights (the uprights). In a triple acrostic a third upright is formed out of interior letters in the cross-lights. The cross-lights may consist of words of varying lengths, but the uprights are obviously constrained to have exactly as many letters as there are cross-lights.
Eckler, A. Ross
"The First Double and Triple Acrostics,"
Word Ways: Vol. 19
, Article 13.
Available at: http://digitalcommons.butler.edu/wordways/vol19/iss4/13