Is this safe and effective or vice versa?

[Hogi]

Hey all, I found an image supposedly helpful in lucid dreaming. My question is, though, is it really at all safe? Even so, is it effective in achieving lucidity? I say this because I haven't heard of exactly pleasant experiences with it. For example, one who tried this felt like his limbs where slowly disjointing and detaching from his body before floating away when he tried this. Another felt like they got restless leg syndrome afterwards. I myself don't even like being paralyzed like this. Has anyone tried this, is it safe and effective? Pros/Cons?