Leyden's own contribution is The elfin king - an atmospheric more robust predecessor of Keat's La belle dame sans merci (1819).
lines from The elfin king
How swift they flew! no eye could view
Their track on heath or hill;
Yet swift across both moor and moss
St. Clair did follow still.
And soon was seen a circle green,
Where a shadowy wassel crew
Amid the ring did dance and sing,
In weeds of watchet blue.
And the windlestrae, so limber and gray,
Did shiver beneath the tread
Of the coursers’ feet, as they rushed to meet
The morrice of the dead.
Come here, come here, with thy green feere,
Before the bread be stale;
To roundel dance with speed advance,
And taste our wassel ale.
You can find the full text of the poem here http://literaryballadarchive.com/PDF/Leyden_2_Elfin-King_f.pdf