Reflection in the Environment

The oldest mirrors made by humans were obsidian mirrors, found in graves associated with the Neolithic settlement of Cetalhojuk. These mirrors were apparently made by taking a piece of obsidian, grinding it down to a circular, flat, or more often slightly convex surface and polishing it until highly smooth and reflective. So this experience of seeing reflections would go deep, deep back into prehistory. But what is the earliest evidence we have of people intentionally making mirrors?