Why does Adi Shankaracharya say magical powers can only be obtained through the Vedas?

Question

As I discuss in this question, by far the most popular school of Hindu philosophy is the Vedanta school, which bases its tenets on the doctrines laid out in the Brahma Sutras, a work by the sage Vyasa that summarizes and systematizes the philosophical teachings of the Upanishads. You can read the Brahma Sutras here. In any case, the beginning of Adhyaya 2 Pada 1 of the Brahma Sutras, Vyasa says this:

1. If it be argued (that from the acceptance of Brahman as the cause of the universe) arises the defect of the (Samkhya) Smritis being left without any scope, then not so, for otherwise will arise the defect of other Smritis losing their scope.
2. And (Pradhana is not the cause) since the others are not met with (in the Vedas and common experience).

Most commentators agree that in these Sutras, Vyasa is refuting Kapila's Samkhya school. Now in this section of his Brahma Sutra Bhashya, the Advaita philosopher Adi Shankarachrya refutes the objection that the philosophical doctrines found in the Smritis of the Samkhya school should be accepted as valid, since Kapila had extra-sensory perception due to his magical powers:

Nor can we assume that some persons are able to perceive supersensuous matters without Sruti, as there exists no efficient cause for such perception. Nor, again, can it be said that such perception may be assumed in the case of Kapila and others who possessed supernatural powers, and consequently unobstructed power of cognition. For the possession of supernatural powers itself depends on the performance of religious duty, and religious duty is that which is characterised by injunction; hence the sense of injunctions (i.e. of the Veda) which is established first must not be fancifully interpreted in reference to the dicta of men 'established' (i.e. made perfect, and therefore possessing supernatural powers) afterwards only.

What Adi Shankaracharya is saying is that magical powers can only be obtained through the injunctions found in the Vedas, so it's invalid to use information gleamed from those magical powers to devise a fanciful interpretation of the Vedas themselves. But my question is, why does Adi Shankaracharya say that magical powers can only be obtained through the injunctions of the Vedas? Are there Yagnas enjoined by the Vedas which yield magical powers?

Now Siddhis or magical powers are mainly discussed by Patanjali's Yoga school; here is what Adhyaya 4 Sutra 1 of Patanjali's Yoga Sutras says about the means of acquiring Siddhis:

janma-oṣadhi-mantra-tapas-samādhi-jāḥ siddhayaḥ

Supernatural powers (siddhis) arise from birth, drugs, mantras, austerity, or yoga (samadhi)

But it's possible that the Vedanta school disagrees with the Yoga school on how to obtain Siddhis. In any case, does anyone know of any references in the Brahmanas or Aranyakas of the Vedas of a Yagna which yields Siddhis?

Answer 1

Yes, there are different kinds of havan- homa and yagya for attaining siddhi, but they are of different kinds not what we generally conduct.

There have been times in history when an entire race of mystical nagas was going to be annihilated in a yagya conducted by Raja JanamaJeya, son of King Parikshit, who was himself son of Abhimanyu, who you ought to know was himself son of the Legendary Arjun of Mahabharata. So here's the story from Wikipedia:

According to legend, Sarpa Satra or Snake sacrifice was a yagna performed by Emperor Janamejaya of the Kuru empire who had ascended to the throne of Hastinapura upon the death of his father Parikshit. The legend states that Parikshit, the lone descendant of the House of Pandu, son of Abhimanyu and grand son of Arjuna of the Mahabharata fame, had died of snakebite. He had been cursed by a sage to die so, the curse having been consummated by the serpent-chieftain Takshaka. Janamejaya bore a deep grudge against the serpents for this act, and thus decided to wipe them out altogether. He attempted this by performing a great Sarpa Satra – a sacrifice that would destroy all living serpents. At that time, a learned sage named Astika, a boy in age, came and intervened to stop the yagna; Astika's mother Jaratkaru also known as Manasa was a Naga and father was also Jarakaru, a saintly Brahmin. Janamejaya had to listen to the words of the learned Astika and set Takshaka free. He also stopped the massacre of the snakes (Nagas) and ended all the enmity with them. From then onward the snakes (Nagas) and Kurus lived in peace. ]]

See? Similarly, there was yagya conducted in the beginning of kaliyug to kill many malechas, who almost were extinct, but then More Malechas were created by Lord Vishnu himself at the behest of kali, who would worship him and propogate kaliyug.

There are similarly many aspects which are unknown to me, many many things which we can't fathom. But it's how it's ought to be, it's kaliyug.

They don't disagree, yoga is part of Atharva veda, but they might be lack the knowledge or proper insight since they never got to sit on other branches of Sanatan dharma so there's confusion. What we read is not the whole story, there are always untold aspects.