Vimaan-Shastra, by Maharshi Bhardwaj refers to "Mani" as "energy-crystal" that used in various operations of Vimaan-yantras involved in power generation, shielding Vimaan from enemy-attacks or weather-disturbances, see distant objects, render Vimaan invisible, energy emission, absorption, attraction, deflection and transduction. This article unveils their properties, synthesis, applications and incorporation in Yantras. These mani were thermally insulating yet electrically conductive and could capture solar and other radiations. There are used as thermal-barrier for protection from extreme heat while allowing efficient electron flow. Most of the mani mentioned in Viman-Shastra were not naturally available, but were synthesized artificially.