Sri Pran Sangli
The Entire Pran Sangali Granth PDF, (Chain of the Vital Breath), an interpretation of Hatha Yoga
I do not know if this book was actually written or not by Guru Nanak Maharaj, or whether it was written after his visit with Raja Shivnabh in Mathaleh, Sri Lanka, or by someone sinister faking it as Gurbani. It contains 20 different shabads. It is found the Bhai Banno Shri Aad Granth Sahib Beer / Khare Vali Bir which is sometimes considered as an un-authorized version of the Adi Granth. Also of interest may be Haqiqat Rah Muqam Raje Shivnabh Ki, which is also found in the Bhai Banno Sahib Beer.
edit: changed link, old link did not work.