What is the mudra to be used when performing Achamanam? How should our fingers be positioned when sipping the water?
Note that scriptures like Manu Smriti do not specify whether we have to form a Mudra in the right hand while sipping water during Achamana.
But some other scriptures do. The Mudra is called the Go Karna Mudra (Go=cow, Karna=ear).
From Devi Bhagavatam 11.16:
25-50. While sipping the Âchaman water on the right hand, touch the right hand with your left hand; otherwise; the water does not become pure. While doing Âchaman, make the palm and the fingers all united and close, of the form of a Gokarna (the ear of a cow) and spreading the thumb and the little finger, drink the water of the measure of a pea. If a greater or less quantity be sipped, then that would amount to drinking liquor
The description given above is quite clear but still I asked previously a question on how exactly to form this Go Karna Mudra (was actually looking for an image for the Mudra).
Quoting from the answer there, which quotes a verse from Viswamitra Smriti (a minor Smriti composed by Rishi Viswamitra):
Angulitraya samyuktam muktAngushtha kanishthakam |
GokarnAkritirityAhu brAhmakarma prakirtitam ||
This verse is more accurately defining the Gokarna Mudra which is to be used during Achamana.
"Angulitraya samyuktam" - So, the three fingers (angulitrayam) - the index, the middle and the ring finger - must be attached/joined (samyuktam) with each other.
"muktAngushtha kanishthakam" - but the Angushtha (or the thumb) and the KanishthA (or the little finger) must be free (mukta) from the association of the three fingers mentioned above.
Using this much details it is quite easy to form the Mudra.
One should make 'Gokarna Mudra' (i.e. cow's ear) while performing Achamanam.
'Nitya karma pooja prakash' by Geeta Press Gorakhpur contains the process.
pdf is available at this link
Attached pic is self explanatory.
In short, it is like this (for those who are not versed with Hindi/Sanskrut text) --
"Make the shape of palm to resemble like cow's ear. Then separate thumb and little finger (last finger) from the rest ones. Other 3 fingers should be touching each other. Sip water from thumb's root which is called as 'Brahma Teertha'."