Thanks. I read this:

"Little is known about his life, and the one book he apparently wrote is lost. His views survive in the short fragments quoted and attributed to him by later authors."

Can you point me to the quotes regarding his inference on the warmth of bodies etc?

I think it is possible that is an inference merely attributed to him by later authors.

In any case the historically earlier Purusha/Prakriti doctrine has a real logical basis.

Either later authors described the arche symbolically as fire or water for example or else they were mistaken.

If mistaken it could be that the earlier insights had become distorted or perhaps they came up with their own similar but wrong ideas independently.

The primordial substance was named by the ancient pre-Buddhist philosophy of Samkhya as Prakriti.

People may say it is water-like or fire-like in various ways. It does not mean H2o or literal fire.

Prakriti is the most subtle broken down/undifferentiated/homogeneous matter/energy possible.

Prakriti is co-eternal with Purusha, primordial consciousness.

Purusha is said to stir up Prakriti and so its evolutes begin. It separates into Tamas, Rajas and Sattva etc.

All else apart from Purusha even thoughts and subtle spiritual bodies and realms are all on the side of Prakriti.