I saw that show on TV and that Indian yogi is an idiot. Elemental mercury is mostly eliminated from the body within a day so one exposure will not kill you but it will poison you to some degree. Mercury in your mouth can be converted to methyl mercury by bacteria.Methyl mercury is 100 times more easily absorbed.
I had 18 mercury Amalgam fillings and was sick for 45 years until I got them removed. There may be substances which will absorb some of the mercury in your gut, such as charcoal, algin, sulfur containing foods, etc. Much of the mercury in your mouth goes into your lungs where it is absorbed into your blood.