Om is the essential symbol in Yoga. It means unity with the supreme, the combination of the physical with the spiritual.
Symbol of the Kalachakra represent Wheel of Time, is one of the most important tantric practices in Tibetan Buddhism. It is a method to understand and harmonize the energies of human beings (microcosm) and the Universe (macrocosm). This practice also contains deep knowledge about the medical and astrological system, as well as yogic practices.