I think all of this is actually pretty promising, there’s a fair amount of agreement between the texts, I am beginning to think it might be possible to sort out the correct attributions here but obviously will need to spend a bit of time with the parallels and chatgpt!
One thing that strikes me about this qoute of yours @yeshe.tenley is that it combines the Pakudha Kaccāyana seven substances with the transmigrations of Gosala (DN2), this is actually quite resonant with the DN1 definition of eternalists:
There are some ascetics and brahmins who are eternalists, who assert that the self and the cosmos are eternal on four grounds.
Santi, bhikkhave, eke samaṇabrāhmaṇā sassatavādā, sassataṁ attānañca lokañca paññapenti catūhi vatthūhi.
And what are the four grounds on which they rely?
Te ca bhonto samaṇabrāhmaṇā kimāgamma kimārabbha sassatavādā sassataṁ attānañca lokañca paññapenti catūhi vatthūhi?It’s when some ascetic or brahmin—by dint of keen, resolute, committed, and diligent effort, and right application of mind—experiences an immersion of the heart of such a kind that they recollect their many kinds of past lives.
Idha, bhikkhave, ekacco samaṇo vā brāhmaṇo vā ātappamanvāya padhānamanvāya anuyogamanvāya appamādamanvāya sammāmanasikāramanvāya tathārūpaṁ cetosamādhiṁ phusati, yathāsamāhite citte (…) anekavihitaṁ pubbenivāsaṁ anussarati.
That is: one, two, three, four, five, ten, twenty, thirty, forty, fifty, a hundred, a thousand, a hundred thousand rebirths. They remember: ‘There, I was named this, my clan was that, I looked like this, and that was my food. This was how I felt pleasure and pain, and that was how my life ended. When I passed away from that place I was reborn somewhere else. There, too, I was named this, my clan was that, I looked like this, and that was my food. This was how I felt pleasure and pain, and that was how my life ended. When I passed away from that place I was reborn here.’ And so they recollect their many kinds of past lives, with features and details.
Seyyathidaṁ—ekampi jātiṁ dvepi jātiyo tissopi jātiyo catassopi jātiyo pañcapi jātiyo dasapi jātiyo vīsampi jātiyo tiṁsampi jātiyo cattālīsampi jātiyo paññāsampi jātiyo jātisatampi jātisahassampi jātisatasahassampi anekānipi jātisatāni anekānipi jātisahassāni anekānipi jātisatasahassāni: ‘amutrāsiṁ evaṁnāmo evaṅgotto evaṁvaṇṇo evamāhāro evaṁsukhadukkhappaṭisaṁvedī evamāyupariyanto, so tato cuto amutra udapādiṁ; tatrāpāsiṁ evaṁnāmo evaṅgotto evaṁvaṇṇo evamāhāro evaṁsukhadukkhappaṭisaṁvedī evamāyupariyanto, so tato cuto idhūpapanno’ti. Iti sākāraṁ sauddesaṁ anekavihitaṁ pubbenivāsaṁ anussarati.They say:
So evamāha:
‘The self and the cosmos are eternal, barren, steady as a mountain peak, standing firm like a pillar.
‘sassato attā ca loko ca vañjho kūṭaṭṭho esikaṭṭhāyiṭṭhito;
They remain the same for all eternity, while these sentient beings wander and transmigrate and pass away and rearise.
te ca sattā sandhāvanti saṁsaranti cavanti upapajjanti, atthi tveva sassatisamaṁ.
Why is that?
Taṁ kissa hetu?
Because by dint of keen, resolute, committed, and diligent effort, and right application of mind I experience an immersion of the heart of such a kind that I recollect my many kinds of past lives,
Ahañhi ātappamanvāya padhānamanvāya anuyogamanvāya appamādamanvāya sammāmanasikāramanvāya tathārūpaṁ cetosamādhiṁ phusāmi, yathāsamāhite citte anekavihitaṁ pubbenivāsaṁ anussarāmi.
with features and details.
Seyyathidaṁ—ekampi jātiṁ dvepi jātiyo tissopi jātiyo catassopi jātiyo pañcapi jātiyo dasapi jātiyo vīsampi jātiyo tiṁsampi jātiyo cattālīsampi jātiyo paññāsampi jātiyo jātisatampi jātisahassampi jātisatasahassampi anekānipi jātisatāni anekānipi jātisahassāni anekānipi jātisatasahassāni: “amutrāsiṁ evaṁnāmo evaṅgotto evaṁvaṇṇo evamāhāro evaṁsukhadukkhappaṭisaṁvedī evamāyupariyanto, so tato cuto amutra udapādiṁ; tatrāpāsiṁ evaṁnāmo evaṅgotto evaṁvaṇṇo evamāhāro evaṁsukhadukkhappaṭisaṁvedī evamāyupariyanto, so tato cuto idhūpapanno”ti. Iti sākāraṁ sauddesaṁ anekavihitaṁ pubbenivāsaṁ anussarāmi.Because of this I know:
Imināmahaṁ etaṁ jānāmi:“The self and the cosmos are eternal, barren, steady as a mountain peak, standing firm like a pillar.
“yathā sassato attā ca loko ca vañjho kūṭaṭṭho esikaṭṭhāyiṭṭhito;
They remain the same for all eternity, while these sentient beings wander and transmigrate and pass away and rearise.”’
te ca sattā sandhāvanti saṁsaranti cavanti upapajjanti, atthi tveva sassatisaman”’ti.
This is the first ground on which some ascetics and brahmins rely to assert that the self and the cosmos are eternal.
Idaṁ, bhikkhave, paṭhamaṁ ṭhānaṁ, yaṁ āgamma yaṁ ārabbha eke samaṇabrāhmaṇā sassatavādā sassataṁ attānañca lokañca paññapenti.
So in DN1 we have the combination of “a hundred thousand rebirths” etc, very much like the 84000 eons, and we have the “eternal, barren, steady like a mountain peak” very much like the substance theory.
I will need to do a fair bit more work to put this all together, but thanks for the great discussion @yeshe.tenley and @Sunyo !!