Glad to see I'm not alone to yawn during deep trance… firstly meditation is a state of being and not something like any action. Once I was doing 1008 times chanting of Shreem Brzee for 21 days, during 5th or 6th day while I was chanting somewhere around 500 I started to yawn and slowly as I was chanting my eyes literally getting closed and it was evening time around 6 only. I'm fully aware but still deep trance inside me. Based on personal experience, Yawning happens to relax all the tension muscles and also mind to experience deep trance. One way to make body also aware is by doing few rounds of nadi shuddi which energizes the body to handle deep trance.
