The Upanishads, Part 1 (SBE01), by Max Müller, [1879], at sacred-texts.com

FIFTH KHANDA.

1. 'The altar is Parganya (the god of rain), O Gautama; its fuel is the air itself, the smoke the cloud, the light the lightning, the coals. the thunderbolt, the sparks the thunderings 3.

p. 79

2. 'On that altar the Devas offer Soma, the king (the moon). From that oblation rises rain 1.

Footnotes

78:3 Hrâduni, generally explained by hail, but here by stanayitnusabdâh, rumblings.

79:1 The water, which had assumed the nature of Soma, now becomes rain.