My apologies, the subject line above is the correct one.
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Dear Madhav and Matthew,
For what it's worth, texts that describe the cakras (tantras & haṭha yoga) routinely add kṣa after the ha. They are placed in the two petals of the āj̇ñā cakra. Padoux discusses the addition of kṣa on p. 156 of his book Vāc:
"...finally the compound phoneme kṣa, the addition of which is sometimes justified on theoretical grounds because it logically fits in a given metaphysical system; but the real reason of its being placed there is difficult to ascertain, except perhaps as a means to have fifty phonemes rather than forty-nine. Naturally, since each phoneme is a form of energy, it is correlated with a deity. There are several texts giving differing lists of these fifty divinized energies."
One could speculate that is was added in order to fill up all the petals in the cakras, but that would imply that the number of petals in seven cakras was fixed before the addition of kṣa.
Padoux, André. 1992. Vāc: The Concept of the Word in Selected Hindu Tantras. Translated by J. Gontier. Delhi: Sri Satguru Publications. Originally published by SUNY.
The book is on SCRIBD:
Regards,
Luis