a body made up of the fire of Yoga...

Prathyapatejomnilakhe samupasthite pashyatmake yoggune pravarte , na tasya rogo na jara na mrityu , pratysay yogagrimay shariram Means—When the perception of yoga , arising from earth, water , light , fire , ether have taken place , then yoga has begun. Unto him does not come disease , nor old age , nor death , who has got a body made up of the fire of Yoga----Shvetashvatara Upanishad