Errantry
Errantry is a three-page long poem by J.R.R. Tolkien, first published in 1933. It was included in Tolkien's short poetry collection The Adventures of Tom Bombadil (1962).
Tolkien invented the meter, which consists of trisyllabic assonances, three in each set of four lines. The second and fourth line in every quartet rhyme, as do the end of the first line and beginning of the second line in every pair. This was so difficult that he never wrote another poem again in this style, though he later did develop another style from this, and the result, through long evolution from Errantry, was Eärendil the Mariner as published in The Fellowship of the Ring (cf Eärendil).