Hacker News
- XKCD Depth Perception http://imgs.xkcd.com/comics/depth_perception.png 6 comments reddit.com
- Intriguing xkcd on depth perception: Has anybody tried this? https://www.xkcd.com/941/ 7 comments reddit.com
- xkcd: Depth Perception - Would this really work? More importantly, who is man enough to try it? http://xkcd.com/941/ 22 comments reddit.com