Butter lamps are a conspicuous feature of Tibetan Buddhisttemples and monasteries throughout the Himalayas. The lamps traditionally burn clarifiedyakbutter, but now often use vegetable oil. The butter lamps help to focus the mind and aid meditation. According to the Root Tantra of Chakrasamvara, "If you wish for sublime realization, offer hundreds of lights”. Pilgrims also supply lamp oil to gain merit. Externally, the lights are seen to banish darkness. Conceptually, they convert prosaic substance into illumination, a transformation akin to the search for enlightenment. Esoterically, they recall the heat of the tummo yoga energy of the Six Yogas of Naropa, an important text for Sakya schools of tantricBuddhism. Each morning Tibetans offer a lighted butter lamp, representing the illumination of wisdom, along with seven bowls containing pure water (or symbolic offerings of washing water, drinking water, flowers, scent, perfumed water, food, and sound) before the images on their household shrine. The butter lamp usually being placed between the fourth and fifth bowls. At funeral ceremonies or when visiting temples and going on pilgrimage to sacred sites, Tibetan Buddhists often light a large number butter lamps together at one time.