blisses again and again. To meditate on innate wisdom, one lets the drop melt all the way down to the chakra at the secret place ("tip of the jewel"). Then one meditates on emptiness and rests in that ecstasy - emptiness meditation. Then one brings the drop back to the crown chakra, which meditates on "the sphere of ecstasy conjoined with emptiness." Tsongkhapa further states: "During the post-meditation periods one must consciously cultivate mindfulness of the experience of ecstasy and emptiness, and stamp all objects and events that appear and occur with the seal of this ecstasy and emptiness. This application causes a special ecstasy to be ignited, which one should foster." Scientific investigation Studies on Tibetan monks and a Western control group have demonstrated the effect of increased thermal power output using the forceful breath technique that depends in part on meditative visualization. In a 1982 study by Benson et al. three monks, who were practitioners of tummo yoga, were researched. All three monks had been practicing tummo for six years on a daily basis. On top of that, they lived in barely insulated, unheated stone sheds. Their skin temperature was measured at different points, namely, around the navel, the lower back, the chest, the left forearm, the left fifth finger nail bed, and lastly, the forehead. In the first monk a temperature increase of 5.9℃ was registered in his finger during a 55-minute tummo practice; the toe temperature increased by 7℃; the air temperature went up from 22℃ to 23.5℃. Finger temperature in the second monk increased by 7.2℃, the toe temperature increased by 4.0℃; the air temperature increased from 16℃ to 19.2℃. In the third monk a temperature increase of 3.15℃ was registered in his finger; toe temperature increased by 8.3℃; the room temperature decreased from 20℃ to 18.5℃ but then increased again to 19.5℃. These results showcase that the practice of tummo yoga can lead to large increases in toe and finger temperature. In a 2002 experiment reported by the Harvard Gazette, conducted in Normandy, France, two monks from the Buddhist tradition wore sensors that recorded changes in heat production and metabolism. However, this study has not been published in a peer-reviewed scientific journal and has been criticized by peers: "The visual effect of steaming sheets reported by eye-witnesses of the g-tummo ceremony cannot be taken as evidence of elevated body temperature. Wet sheets wrapped around