How did these three pre-Socratic materialists - Anaximander, Heraclitus, and Democritus - identify the nature of ultimate reality?

Pre-Socratic Materialists

Early Greek philosophers who believed that the physical world is composed entirely of matter without the influence of supernatural forces.

Ultimate Reality

A concept in various philosophical and religious traditions referring to the most fundamental nature of existence, beyond which no further causal explanation can be sought.

Anaximander

An early Pre-Socratic philosopher from Miletus in Ionia, notable for his work in cosmology, geography, and biology.