The Speculum Regale
Speculum Regale, The (L)
The Speculum Regale (The King’s Mirror)(a) was written in Norway around 1250 AD. Bramwell notes that in it, Ireland was identified with Atlantis[195.181].
Bramwell was mistaken, referring to a land-under-the-waves (Tir fo thuinn) which is a term sometimes applied to Hy-Brasil a mythical sunken land to the west of Ireland.
(a) https://www.archive.org/stream/kingsmirrorspecu00konuuoft/kingsmirrorspecu00konuuoft_djvu.txt