दीर्घप्रणवमेवं हि योगिनामेव हृद्गतम् । मकारं तंत्रितत्त्वं हि ह्रस्वप्रणव उच्यते १४ ।
The long Pranava (Om) is indeed the one that resides in the heart of yogis. The 'M' sound (Makara) is the essence of the Tantric principle. The short Pranava is also called the 'Hrasva Pranava'.