Charward, I assume you are looking for the fourth marker, as that's the only one I remember that you fall going after. Here is a quote from the advice that I gave someone else who was having trouble here: "Here's a quote from Becky, whose advice I used to get that last marker: 'Are you talking about the marker near the library? I found it by walking along the edge of the cliff until I could hear the marker sound. Then I looked down and edged my way closer until I could see it (as you are facing AWAY from the library, I think it is near the left part of the cliff and is down near the bottom of the cliff). I did not have to fall to click on it, though once I did click on it I immediately fell.'"
One last note, I don't know if the marker is always in the same place or not, but for me it was down low and behind me, so I almost missed it...