I was camped at Little Yosemite Valley with some friends, preparing to hike Half Dome the next day. While cooking dinner on top of a bear box, I reached down to pick up something. A dark shape flashed from under the box, touched my hand, and disappeared. I pulled back and saw two trickles of blood. 

My friend probed beneath the bear box with a trekking pole, and a 2-1/2-foot rattlesnake emerged. My girlfriend called 911 and was able to reach dispatch in the valley far below us. They wanted to send a helicopter, but couldn't because it was dark. 

Plan B was to hike down the trail to meet the search-and-rescue team that was hiking up from the valley. Soon my toes, lips, cheeks, and scalp started to buzz. My hand and arm started to swell. Then the granite walls started turning colors and changing size. I decided to keep my eyes down on the trail. 

Two and a half miles along the trail, we met the search-and-rescue team. My arm was now swollen to the elbow. They started me on an antivenin drip and wheeled me 2 steep miles to the valley floor.

By 4 a.m. I was in a Community Hospital, where I stayed for two days. The Total tab was $70,000, $43,000 of which was for the anti-venin. (Luckily I had insurance.) My arm and hand made a full recovery, and today I only have two small fang scars.