I totally agree with Bhain jee's post above. Its Naam Abhyaas that matters and not the Aasan you sit in, while doing Simran. Gurbani covers all aspects, causes and effects of Naam but does not state any importance to an Aasan while doing Simran. Quite often many people influenced by Vedant and other Hindu practices promote sitting in certain postures to concentrate on Naam but Gurbani says that Naam should be chanted all the time whether you are sitting, lying down, standing, walking, working or not-working.
As far as Gurmat Naam Abhyaas Kamaayee is concerned, all Aasans of Yoga are useless and hold no importance in Gurmat. Some ignorant Sikhs today are giving too much importance to Yoga especially that preached by the Yoga-guru Raamdev. To cure themselves of diseases, they place more faith in his Yogic teachings than Gurbani and Naam. They forget that Sidh-Gosth Baani is totally dedicated to rejecting the Yogic philosophy and proves the supremacy of Gurmat over it.
Guru Sahib Kirpa Karan.
Kulbir Singh