Mercury Nitrate

Which, should be noted, is not the mercury show in the picture. Mercuric nitrates are a white/yellow dry powder that is the result of mixing mercury with nitric acid. The process of making mercuric nitrates, and carroting itself, both result in rather toxic fumes that you really should not breathe in.

Handling liquid mercury is basically almost harmless as it absorbs through the skin really slowly and doesn't produce much vapours. Putting it in acid, heating it up, and putting the cloth treated with it in an oven is not.