Bhagwad Gita
Chapter 8, Verse 12
सर्वद्वाराणि संयम्य मनो हृदि निरुध्य च।
मूर्ध्न्याधायात्मनः प्राणमास्थितो योगधारणाम्।।8.12।।
The yogic situation is that of detachment from all sensual engagements. Closing all the doors of the senses and fixing the mind on the heart and the life air at the top of the head, one establishes himself in yoga.