At this late hour (GMT +2), and one not without significance, I feel blessed to be able to have such meaningful conversation in a world full of meaningless fantasies.
Again Pandara said what was needed to be said. I had recieved this impulse to share the wisdom I found in the Upanishads, than I noticed that Asuri did the same. Still, because by chance (I strongly believe there is no such thing but allow me to use the concept just to share what I think of it) the book Yoga in Upanishads got into my hands (it was not hard as it has been on my shelf for decades) I’d further point to the very ones (Upanishads) what deal with the movement of vital forces, and relate to breathing. These are:
[B]Yogatattwa[/B]
[B]Dhyanabindu[/B]
Yogakundalini
Ksurika
[B]Hamsa[/B]
Amrtandanda
Amrtabindu
Mahavakya
I bolded out the ones I am sure they deal with pranayama, that does not mean the others do not, only that I had no sufficint time on my hands to read them. For example, and related to your question Willem, Yogatattwa Upanishad says:
[I]63. Then sitting in a secluded place, he should repeat Pranava (OM) with three Pluta-Matras (or prolonged intonation) for the destruction of his former sins.[/I]
[I]64. The Mantra, Pranava (OM) destroys all obstacles and all sins. By practising thus he attains the Arambha (beginning or first) state.[/I]
[I]65-66. Then follows the Ghata (second State) – one which is acquired by constantly practising suppression of breath. [B]When a perfect union takes place between Prana and Apana, Manas and Buddhi, or Jivatma and Paramatman without opposition[/B], it is called the Ghata state.[/I]
Now, thistranslation is not the most succesful, as it fails to justify the various terms it uses, and thus, the connection between them fades, becoming incomprehensible. Because I have the luck of having a great translation, romanian that is, what not only uses Prana and Apana, Manas and Buddhi, Jivatma and Paramatman but substitutes inhalation-exhalation, mind and intelligence, individual soul(spirit) and universal soul(spirit) - we need not to dwell on if these transaltions are 100% correct or not, but rather on what this succesion evokes in us. The translation I use, has the merit of linking not just the above mentioned pairs, but it also links the couples to each other. Thus, the text of Upanishad teaches not just the need to unite Prana with Apana but the need to realize the union(connection) between inhalation-exhalation and mind-intelligence, and what is more important, inhalation-exhalation and God-soul, to translate it to western terms. That this translation is not arbitrary, is shown also in that part of the Upanishad what equates Brahman to inhalation, Vishnu to retention, and Rudra to exhalation. (Dhyanabindu Upanishad, verse 21)
What this tells me, is that we need to be able to pass a mechanicist conception of the human being, where breathing is the result of the central nervous system. What these ancient texts tell us, but in our materialist age we often fail to recieve, is that the spiritual preceeds the material/ sensorial. It is not the complex biological machine what makes us breath, but the spiritual (divine) acting through the higher principle of Life is what puts our breathing process in motion. When we are asked to realize the union, our task is not that of control, but that of becoming aware of the very sacred and divine nature of breathing, and trough it, to realize our very own divinity. Not by intellectual accept, or the inflation of our ego, but as a personal revelation of truth.
I did dare to include in the quote verse [I]64. The Mantra, Pranava (OM) destroys all obstacles and all sins.[/I]
As for a great part of the world prepares for a certain feast, let this final AUM stand here for our obstacles and errors.
AUM