Linga Mudra is performed by interlocking all the fingers by both the hands with little finger of the left hand to the down most and keeping the Thumb ( Fire ) of the right hand upright. Join the tip of the left hand thumb to the tip of the left hand index finder making a circle abound the right hand thumb. This is performed by sitting straight in Padmasan or Sukhasan.
By performing this mudra, you can get relief from severe cold. During winter, when it is cold outside, you wear sweaters and heavy clothes, but still you feel for more heat. Just perform this mudra for 10-15 Minutes and you feel the heat. This will increase your body temperature from inside.
Nice posting. Do you know about these yoga books?