Sashti Tantra is a text formulated the Samkhya philosophy. The origin of Samkhya dates back to the Vedas. But to trace its origin and development is perhaps one of the most difficult tasks, as most of the ancient writers and the texts are lost to antiquity, Shashti Tantra being one such text.
Sashti Tantra, “the science of sixty topics”, seems to denote a text which formulated the Samkhya system of philosophical speculation. It is also held that Sastitantra may even be a proper name for the system as a whole.
The sixty topics discussed here are – mulikartha (ten principal topics), viparyaya (five fundamental misconceptions), asakti (twenty eight dysfunctions), tusti (nine contentments) and siddhi (eight attainments).
The text can be inferred through many references to it in Samkhya literature and other texts of other philosophical schools.
In a long passage attributed to Devala (1st century BCE) in Aparakartika on Yajnavalkya Smriti, the term Tantra is mentioned in the context of a Samkhya text.
In Jayamangala commentary (7th century CE) the oldest one on Samkhya Karika, the passage “Sashtitantrakhyam Sastikhandakrtam” indicates the extent of the work to sixty chapters.
Vacaspati (9th century CE) in his Tattvavisaradi identifies a quotation in Vyasa’s Yogasutra Bhashya (IV.13) as deriving from a work entitled Sastitantra.
Regarding the authorship of Sashti Tantra various references are found.
Yuktidipika indicates in its introductory verses that the scheme of Sashti Tantra was handed down by Kapila himself.
In the work Kalpasutra of the Jaina School, Mahavira is referred to as Sastitantravisarada. In the commentary the author Yasovijaya takes it to the Sashtitantram Kapilasastram.
There is a reference to Kapila Sashtitantra in the Jaina work Avuyogadvara-sutra, where the works of rival schools are censured.
In his Brahmasutra-bhashya, Samhara refers to Tantrakhya-smriti as Paramasrshipranita, in which Paramarsi is identified with Kapila by Vacaspati.
Panchasikha is also attributed with a massive treatise in verse called Sashtitantra, but on comparing the views ascribed to him in the Mahabharata, they are found to be at variance with each other.
Varsaganya is also attributed with the work called Sashti Tantra by Vacaspati in his Brahmasutra-bhashya (II.1.3). But this quotation is in a prose form and the source of it is from a Yogasastra.
On account of the above mentioned complexities regarding the authorship and the nature of the work, scholars suggest that the original verse or aphorism of Kapila was greatly expanded by Panchasikha and finally revised into a verse cum prose form by Varsaganya.
There are also opinions that Tattvasamasa-sutra ascribed to a later date by western scholars, could have been Mula-Sastitantra ascribed to Maharishi Kapila, as the text follows the scheme of pre Samkhya Karika, and was later expanded and revised by Panchasikha and Varshaganya.
Source - Encyclopedia of Hinduism Volume IX - IHRF page 302 - 303