IRAA, PINGALAA, SUKHMANAA
In Yoga tradition, these are three imaginary vein.
Iraa is a name given to a vein somewhere between left nostril and spinal cord; the vein on the right side of nostril, has been called Pingalaa and a vein which links nostrils, spinal-cord and brain has been given the name Sukhmanaa.
These are the veins supposed to be helpful in practice of Yoga.
The refeences to Ira Pingalaa Sukhmanaa in the Sikh literature, are relative and metaphorical and not conceptual (and only in order to reject them).
In Sikhism, only remembering God is real Yoga.
(Dr Harjinder Singh Dilgeer)