Maelgwn Gwynedd was a king of Gwynedd (d.547 AD), said by Geoffrey of Monmouth to be a High King of Britain. Among many other tales of his lifetime, one tells of how he demanded that the many lesser kings of North Wales should accept him as their overlord. On the tidal sands of what is still called Traeth Maelgwn, on the edge of the river Dyfi near Ynyslas, he organised a competition to see who could remain seated in their chairs for longest as the tide came in (cf Cnut/Canute). However, he had subtly increased the odds of his winning by fitting his chair with waxed bird wings - which nobody noticed until it was too late - and which lifted him up with the tide and ensured his victory.
See http://www.britannia.com/bios/ebk/maelgggd.html for a history Maelgwn Gwynedd.Ynyslas as a Health Resort
There's a plaque on a house in Ynyslas that records the fact that in 1891 Ynyslas was opened up as a "Health Resort". The driving force behind this was a William Gregson from Bolton, and the house is called Gregson House to this day. I've not been able to find out much about him yet, except that he took out a 99 year leasehold in Sep 1870 on "Land near Lerry", and that in 1910 he was reported to be "of Bolton and Moelynys, Borth". I wonder what happened to his plans for the Health Resort?