On July 8, 2000, about 1335 hours Pacific daylight time, a Stinson 108-2, N264C, sustained substantial damage when it departed the runway and nosed over during takeoff from Douglas County Airport, Minden, Nevada. The owner operated the airplane as a demonstration flight under the provisions of 14 CFR Part 91. The certified flight instructor and private pilot passenger were not injured. The flight originated in Carson City, Nevada, about 1310. Visual meteorological conditions prevailed and no flight plan was filed. The pilot stated they flew to Minden and completed a landing. The airplane was taxied back for departure on runway 34. He stated the airplane yawed to the left as he expected after application of power and he corrected with right rudder. He said the takeoff was proceeding normally when the tail suddenly veered to the left and then to the right. He thought he encountered a dust devil or gust of wind. At this time the airplane was 2 to 3 feet in the air and headed about 50 to 70 degrees to the runway heading. He did not feel it prudent to attempt to realign with the runway and continued straight ahead. About 50 feet past the edge of the runway, the propeller and wheels began contacting sage brush that was 2 to 5 feet high. The airplane descended into the ground and nosed over onto its back. The pilot noted the density altitude was nearly 7,000 feet. He also noted that subsequent inspection revealed the air intake was almost completely filled with sage brush needles.