Do you know any sources for ancient dream interpretation texts?

[BrianSoddingBoru4]

The "symbolism" is what the interpretation materials are for. Say you dream about a "fish"; the fish symbolizes something in the dream, the ancient text tells you what it means.

Dreams are intensely personal.  If you think a fish means a fish, you're right (although it won't mean a fish to everyone).  If you think it means a concrete abutment at the west  end of a suspension bridge, you're right (same caveat).

Boru