Sumantri (also spelled Soemantri or Soemantri Brodjonegoro) is a sharp mountain in the western Sudirman Range (New Guinea), it rises 4,870 metres (15,978 ft). The peak is approximately 2 km northeast of Carstensz Pyramid (4,884 m), the highest mountain of Oceania. The north side of Sumantri is dominated by tremendous cliffs that wrap around onto both the eastern and western sides of the mountain. Remnants of the once mighty North Wall Firn still cling tenuously to the southern aspects of the peak. It is unlikely that this ice will last for more than the next fifteen years.
Ngga Pulu was first climbed by a Dutch expedition in 1936 (Anton Colijn, Jean-Jacques Dozy and Frits Wissel), so it is possible that they made the first ascent of this peak. If they in fact climbed the eastern peak, then the first ascent of Sumantri was made by Heinrich Harrer, Phil Temple and Russel Kippax on the same expedition as their Carstensz ascent in 1962. Back then, due to Glacier ice, the ordering and elevation of the peaks was different than it was today.
The mountains of Central New Guinea are being formed as the Australian and Pacific Plates collide, resulting in both subduction and uplifting. The rocks at the surface for the peaks in this range are made of limestone, as a result, even though the summit block of the peak looks extremely daunting, it is actually an fairly easy scramble.