In Chapter 10 of Uncharted 4 there are 16 rock cairns dotted around Madagascar, and you need to knock them all over to earn the hidden Not a Cairn in the World trophy. You can do this by either driving through them in your jeep, or getting out and performing a melee attack on them. Make sure you collect them in the order below as there are several points of no return during the chapter, but if you do miss any then you can replay the chapter and pick them up on your next playthrough.
Straight ahead of you at the start of the chapter.
Along the track as you approach the waterfall area.
After you pass under the rickety bridge, at the bottom of the muddy slope.
At the top of the muddy slope before crossing the bridge.
On the other side of the bridge, to the left under a tree.
After driving up a rock with lemurs on it and spotting the tower ahead.
Next to the small waterfall and sliding rock you drive up.
After using the winch for the first time and spotting the volcano, down the watery path heading left towards the ruins.
After dropping into the next area, opposite the cave on the right hand path.
Once you've 'fixed' the next bridge and driven up the muddy slope, up the hill to your right.
Straight ahead of you when you see the Shoreline trucks in the distance.
Up the hill at the far side of the area, near the rocky hill to the left.
At the top of the rocky hill to the left in the same area.
Heading up the hill towards the Beacon Tower, just before the ornate pillars.
On top of the rocks opposite the Beacon Tower.
On the narrow track at the other side of the drawbridge.
At this point you should unlock the Not a Cairn in the World trophy - congratulations!