This topic may not exactly fit with this board, but deals with ancient times so...
I was wondering if anyone could shed any light on ancient practice of meditation/yoga - I'm quite sure that there was some Egyptian/Sumerian folklore pertaining to these things... Theories are welcome.
In early insular Celtic culture, people known as filidh (sacred ecstatic poets) practiced several forms of meditation and breath control, at least from what we can tell by early (post-Christian) texts. Most of what we have is vague description and conjecture, rather than actual instruction in such things, unfortunately. We do, however, have mentions of a meditation referred to as "stone on the belly", which was probably a meditation to help with breath control technique for chanting of poetry and charms. There are references to dream incubation type meditations, some of which were designed to take up to 9 days in ritual for vision-seeking. These include the "imbas forosnai" ritual and the "tarbhfeis". The latter involved wrapping oneself in the skin of a freshly slaughtered yellow bull, so you probably don't want to try that one at home
Meditation was used in sweat-houses among the Scots and the Irish until at least the 18th century. One writer, Martin Martin, in his 1717 account of a trip to the Highlands and Islands, refers to the use of the sweat-house, where healing herbs were use;, apparently quartz crystals were part of this process, and massage was used on the person seeking healing. The patient was then advised to meditate until they acheived peace.
Meditations that resulted in otherworld journeying are also a part of early Celtic tradition.
One early text (7th century CE with 11th century commentary) describes in part the training of the fili. It is commonly referred to as the Cauldron of Poesy text, and discusses the three internal cauldrons in every person and their effects and motions. There's an article that includes my translation and commentary on this text at my website, <a href="http://www.seanet.com/~inisglas" target="_blank">The Preserving Shrine</a>, if anyone is interested in taking a look around.
I could speak in greater detail, but I've just moved into a new house and my library is still largely in boxes. The article on my website does go into some depth, however.