Much of yoga is based on memory and visualisation. From imagining yourself as a series of detailed deities holding various items and with specific attributes to visualising special temples at specific points on the spine, through to even placing letters on your own body parts. Most of the yogic practices would be familiar to European Hermetic Memory masters. You can even find some examples of what we would see as memory wheels.
One great example of this can be found in the Kubjika Upanishad in a practice sometimes called ‘Bowing to the Eight Directions’ in which the practitioner turns his attention to the heart.
The practitioner visualises an 8-petalled lotus within the space in the heart, and directs attention to each of the 8 petals in turn. Each petal has an associated passion like hatred or lust, which (when on the petal) the yogi must overcome using the mantra. Once he has passed the test, he can finally stand in the middle of the flower, being beyond passion. It is implied that the sins could then be combined in patterns to supply combined passions or challenges that the ascetic might need to wrestle with in life. Perhaps he may have a form of angry jealousy, or prideful love. Could a sense of lazy spitefulness catch him out? In the end, could he combine them all for the ultimate test?
By rotating this memory wheel in his heart, the yogi can test himself in a way it would normally take many lifetimes to undertake and achieve a complete Vairagya or Yogic dispassion, allowing him to ascend to higher consciousness.
Could this be a hint at how some practitioners used the letters in other Chakras?