But standing high aloft, low lay thine eare,
  And there such ghastly noise of yron chaines,
  And brasen Caudrons thou shalt rombling heare,
  Which thousand sprights with long enduring paines
  Doe tosse, that it will stonne thy feeble braines,
  And oftentimes great grones, and grieuous stounds,
  When too huge toile and labour them constraines:
  And oftentimes loud strokes, and ringing sounds
From vnder that deepe Rocke most horribly rebounds.

The cause some say is this: A litle while
  Before that Merlin dyde, he did intend,
  A brasen wall in compas to compile
  About Cairmardin, and did it commend
  Vnto these Sprights, to bring to perfect end.
  During which worke the Ladie of the Lake,
  Whom long he lou'd, for him in hast did send,
  Who thereby forst his workemen to forsake,
Them bound till his returne, their labour not to slake.

In the meane time through that false Ladies traine,
  He was surprisd, and buried vnder beare,
  Ne euer to his worke returnd againe:
  Nath'lesse those feends may not their worke forbeare,
  So greatly his commaundement they feare,
  But there doe toyle and trauell day and night,
  Vntill that brasen wall they vp doe reare:
  For Merlin had in Magicke more insight,
Then euer him before or after liuing wight.

The Faerie Queene, Book III, Canto III