Yoga Sutra II.46
strira sukam asanam.
Asana is a steady, comfortable posture.1
I was practicing some yoga postures on Easter morning when Sasha (short for Alexander), my 17-month-old son, crawled over and starting climbing on me. It seems like when I want to hold him he just wants to crawl away, but when I let him be to do some yoga or something then he wants to climb all over me demanding my full attention. He is not walking yet, so this morning he decided to use me in shoulderstand (sarvangasana) as a prop to stand up. He finds it hilarious when I try to practice yoga postures. Although my shoulderstand is far from perfect as you can see in the picture, with Sasha hanging on to my pants laughing at me - this was a perfect posture for a perfect moment.
A comfortable and steady posture helps prepare the mind for meditation. The various postures help us tune into the moment, by acting like a harness to yoke the wandering mind to the body. With each changing posture I'm reminded of how the moment passes and I can not cling to it because it will always slip through my fingers and crawl away just like Sasha when I try to cling to him.
1. translated by Sri Swami Satchidananda. Integral Yoga. (pp. 178-179).