Rudraksha -  Buddha wore  these  Beads ,so did  Gandhi , Dalai  Lama  &  Indian  Yogis.

Yantra literally means "instrument". A Yantra is a geometric design acting as a highly efficient tool
 for contemplation, concentration and meditation. Yantras carry spiritual significance, and point the user to higher levels of consciousness.
The Yantra provides a focal point that is a window into the absolute. When the mind is concentrated on a single, simple object (in this case a Yantra), the mental chatter ceases. Eventually, the object is dropped when the mind can remain empty and silent without help. In the most advanced phases, it is possible to attain union with God by the geometric visualization of a Yantra. The Yantra is like a microcosmic picture of the macrocosm. It is a focusing point and an outer and inner doorway. The Yantras are often focused on a specific deity and so by tuning into the different Yantras you can tap into certain deities or creative force centers in the universe.