In this excerpt from the Taittiriya Brahmana of the Yajur Veda, a story is told involving Indra and the sage Bharadvaja. Bharadvaja spent three successive births practicing Brahmacharya in order to learn the Vedas fully, and wanted to take a fourth birth to do the same, but then Indra told him that this is futile since the Vedas are infinite. And then Indra taught Bharadvaja something called the Agni Savitra, which led to great results in the afterlife:
Bharadvaja lived through three lives in the state of a religious student (brahmacharyya). Indra approached him when he was lying old and decrepit, and said to him: 'Bharadvaja, if I give thee a fourth life, how wilt thou employ it;?' 'I will lead the life of a religious student,' he replied. He (Indra) showed him three mountain-like objects, as it were unknown. From each of them he took a handful: and, calling to him, 'Bharadvaja,' said, 'These are the Vedas. The Vedas are infinite. This is what thou hast studied during these three lives. Now there is another thing which thou hast not studied, come and learn it. This is the universal science.' He declared to him this Agni Savitra. Having known it he (Bharadvaja) became immortal, and ascended to the heavenly world, to union with the sun. He who knows this ascends to heaven, to union with the sun. This is the triple Vedic science. He who knows this conquers a world as great as he would gain by the triple Vedic science.
My question is, what is this Agni Savitra that Indra taught to Bharadvaja? The reason I'm interested in it is that the Advaita philosopher Vidyaranya discusses this story in this excerpt from his Jivanmukti Viveka, and he says that Indra imparted to Bharadvaja knowledge of Saguna Brahman:
[Shastra Vasana] is of three kinds... The first kind of this vice is seen in Bharadvaja who, though he applied himself to the Veda in three successive lives, began, on being incited by Indra, to study the remainder of Vedic lore even in the fourth. As this kind of study has no end, and is, therefore, impossible to accomplish, it is set down among impure Vasanah. Indra, of course, cured Bharadvaja of this vice by enlightening him into the knowledge of Brahman with character. This has been described in the Taittiriya Brahmana.
That makes the Agni Savitra sound like it's akin to the 32 Brahmavidyas, lessons found in various Upanishads which can lead you to Brahman if you meditate upon them. So what information about about Saguna Brahman (i.e. the supreme Brahman according to non-Advaitin schools) did Indra impart to Bharadvaja?