The Mabinogion is a mess of misconstrued mythology, a minefield of mistranslation and misinterpretations. It’s also the font of all fantasy, a literary sub-genre that did not have any following before Lady Charlotte Guest presented her loose translation, first published in seven volumes between 1838 and 1845. Much effort was put into making them read as a cohesive, integrated story, which they were not. They were compiled from many traditional tales told in the Welsh language dating right back to the earliest bardic tradition and originate in an ancient culture that spanned pre-Roman Briton and Eire.
There was once a bright-white cow which travelled round the world, giving milk enough for all comers. Whoever drank of her milk immediately became wise.
The tales surrounding this, rather unassuming, standing-stone are taller than the stone itself.