The Mandala Thogchag is the sixty-first treasure that can be found in Uncharted 2: Among Thieves.
The Mandala Thogchag is found in Chapter 18 - Heart of Ice. This treasure is pretty well-hidden. The key to grabbing it is the third and final spinning cylinder the player comes across when crossing the gap. When reaching the third cylinder, the player should climb up to the very top of it and begin to rotate along with it. Attached to one of the wooden boards (that serve to knock the player down) is the treasure. The glint can be seen clearly, but to actually grab it successfully, the player will have to rotate just underneath the wooden board and grab it as the on-screen prompt indicating a treasure is nearby shows up.