Vajra Deha is an unusual type of yogic achievement mentioned
in the Yogasutra. Vajra deha is a human body, which has attained the strength
of a diamond.
The human body is made out of Panchabhutas or five elements.
When the earth element responsible of hardness attains special dominance, the
body can attain the hardness of a diamond.
The belief is that such a body becomes so strong that no
weapon made of any metal can harm it.
Sage Dadhici is believed to have attained such a body by the
power of his penance.
It is also believed that in Ayurveda there are specific
medicines that can give a person Vajra Deha.