What I did, was to flip out my scanner and just keep running it over the terrains whereever I was. In that way, I could quickly see if something lighted up in bright orange or red because it had not been scanned.
Why don“t you just consult the guide found at cube.ign.com or gamefaqs.com?
In any event, I recall that there is one runic symbol near a couple of crates inside some weeds. Next, there is one right in front of the bridge which you jump onto in order to proceed higher on the ledges. Then there is one on the tree higher up, and finally one on the the last ledge you stand on before jumping up to the sunchamber acces gate!
Hope that helps. Otherwise it will help others who may not yet have cracked that puzzle.