On September 8, 1907, the Kaufmanns guided Kellas in an attempt to reach the summit of Simvu (22,800 ft.), but, encountering a snowstorm, they were forced to abandon the climb at 19,000 feet. Two days later they attempted the summit again, but the Kaufmanns again abandoned the ascent, considering the snow too dangerous at 20,700 feet. A third attempt on September 30 that began at 2 AM and involved crossing the Zemu glacier by moonlight was also abandoned because of deep, soft snow and inclement weather at 20,000 feet. In his various reports to the Alpine Club (London), Kellas says that the Kaufmanns turned back because of heavy snow and storms. Although he later explains that the Swiss guides were unsatisfactory, he never directly says the Kaufmanns suffered from altitude sickness; however, Himalaya summits are predominantly over 20,000 feet, and the Kaufmanns were accustomed to heights of 10,000 to 16,000 feet, so that Swiss guides were not as acclimatized to such heights as the native sherpas.