[ryandv]

    You must learn to sit perfectly still with every muscle tense for long periods.

    Various things will happen to you while you are practising these positions; they must be carefully analysed and described.

    Note down the duration of practice; the severity of the pain (if any) which accompanies it, the degree of rigidity attained, and any other pertinent matters.

    When you have progressed up to the point that a saucer filled to the brim with water and poised upon the head does not spill one drop during a whole hour,
    and when you can no longer perceive the slightest tremor in any muscle; when, in short, you are perfectly steady and easy, you will be admitted for examination;
    and, should you pass, you will be instructed in more complex and difficult practices.

- Aleister Crowley, Liber E vel Exercitiorum, 1911. https://hermetic.com/crowley/equinox/i/i/eqi01005

[mionhe]

I assumed this was referring to a simple seated position, but I was incorrect. He had people in some odd poses for meditation. Thank you for posting the source.