A chaturtha asked me if mantra-s in the shruti were entirely inaccessible to him. I told that if looked hard enough in the texts to which he had adhikAra he could find enough to be moderately aware of the contents of the shruti if not its praxis, which indeed is largely the domain of the dvija-s. The vedic material embedded in the itihAsa-s, the harivaMsha, and the purANa-s has been of some interest to me for a while, though I have never gotten around to systematically studying it by computational means. Kane and Apte have written on this topic, with the former precisely touching on this issue of the adhikAra of the shUdra and the shruti. A learned clansmen, a student of the first veda, informed me that Apte is supposed to have had a student in the city of my youth who did such a study quite systematically for the great epic but I have never been able to access his dissertation on the same. There are, of course, a few famous examples, which we have covered at length on these pages before – the hymn of the ashvin-s and the praise of indra. Some are intended quotations, while others like the spell of queen kaushalyA are a mixture of vedic and later elements. The intended quotations, as Apte points out, are labeled with the qualifiers such as:
imAm shrutiM udAharet
nidarshanaM chAtra bhavati
ityapi shrUyate shrutiH
yastaM veda sa veda vit
In the old days I used to have a debate with some acquaintances over the possibility of a para-vedic tAntric system. It was in this context that I observed that the itihAsa-s and the harivaMsha cite vaidika mantra-s as such, but rarely, if ever, furnish a conventional tAntrika mantra [Footnote 1]. This to me indicated that the conventional tAntrika system post-dates the itihAsa-s though they do overlap with the majority of the purANa-s as they survive today. Hence, I tend take the stance that the tAntrika mantra shAstra is largely an evolute of the late vaidika system rather than being a survivor of a para-vedic system [Footnote 2].
Let us consider some well known citations from the bhArata. One chapter that is replete with citations is the lecture of kR^iShNa to arjuna on the nature of agnIShomau and nArAyaNa (vulgate MBH 12.343). It is definitely a highly interpolated section with at least 3 major players: 1) brAhmaNa-s trying to assert their superiority in the brahma-kShatra alliance. 2) vaiShNava-s trying to establish nArAyaNa-paratvaM and 3) shaiva-s trying to establish rudra-paratvaM. Yet all manuscripts contain the vedic citations in some form and the core of the narrative is actually that of agni-Shoma which is directly based on the vedic citations. This is evidenced by the original question of arjuna to kR^iShNa:
agnIShomau kathaM pUrvam ekayonI pravartitau |
eSha me saMshayo jAtastaM chhindhi madhusUdana ||
How did agni-Shomau, in days of yore, get established in the same original source? Such a doubt has arisen, please clear it O madhusUdana.
It is in answering this that kR^iShNa explains the transformations of nArAyaNa and cites some vaidika mantra-s as pramANa-s:
nidarshanamapi hyatra bhavati:
nAsIdaho na rAtrirAsIt | na sadAsIn nAsadAsIt
tama eva purastAd abhavad vishvarUpaM ||
mantravAdo.apI hi bhavati:
tvamagne yaj~nAnAM hotA vishveShAM hito devebhir mAnuShe janeti ||
nidarshana.n chAtra bhavati:
vishveShAm agne yaj~nAnAM hoteti | hito devair mAnuShair jagata iti ||
 stotras to tAntrika deities might be found but they lack tAntrika mantra-s; the harivaMsha might preserve proto-tAntric mantra elements in the context of ekAnamshA as noted before.
 in more general terms by extension I also believe that Talageri’s idea of the vaidika system being restricted to the pUru-s as being erroneous – the composition of the RV might have been dominated by the pUru-s but this hardly means that the other Indo-Aryans and Iranians did not follow a “vaidika” system.