Parad or Mercury is regarded as sperm (seed) of Lord Shiva in ayurveda. Parad shivling is considered as Lord Shiva and is regarded as of wonderful changes and powers.Lord Shiva said to MAA Parvati that one who worships Parad shivling is not suffered with poverty and nor fear of death.All material things like fame, name, post, power and wealth can be detained by worship of this.This is self praan pratishthit so it is not necessary pratishtha specially. It is worshiped by ' MAHA MRITUNJAY MANTRA'.