On April 26, 2001, approximately 1200 Pacific daylight time, a Maule M-7-235, N126DP, nosed over during a landing on soft terrain near the edge of Summer Lake, Summer Lake, Oregon. The private pilot, who was the sole occupant, was not injured, but the aircraft, which was owned and operated by the pilot, sustained substantial damage. The 14 CFR Part 91 personal pleasure flight, which departed Bend, Oregon, about 45 minutes earlier, was being operated in visual meteorological conditions. No flight plan had been filed. The ELT, which was activated by the accident sequence, was turned off at the scene. According to the pilot, he performed a soft-field landing in an area that had previously been covered by the lake when water levels were higher. Although the touchdown was uneventful, as the aircraft slowed, the main gear sank into the soft terrain and it nosed over onto its back. The pilot said he had not taken any action to determine how soft the terrain was prior to landing.