The Upanishads, Part 1 (SBE01), by Max Müller, , at sacred-texts.com
1. The hiṅkâra is, he rubs (the fire-stick); the prastâva, smoke rises; the udgîtha, it burns; the pratihâra, there are glowing coals; the nidhana, it goes down; the nidhana, it is gone out. This is the Rathantara Sâman as interwoven in fire 3.
2. He who thus knows this Rathantara interwoven in fire, becomes radiant 4 and strong. He reaches the full life, he lives long, becomes great with children and cattle, great by fame. The rule is, 'Do not rinse the mouth or spit before the fire.'
29:3 The Rathantara is used for the ceremony of producing fire.
29:4 Brahmavarkasa is the 'glory of countenance' produced by higher knowledge, an inspired look. Annâda, lit. able to eat, healthy, strong.