taitiriya upnishad : chapter 3

together we may attain glory, together to the radiance of holiness. hereupon we will expound next to the secret of sanhita whereof there are five capital; concerning the worlds; concerning the shining fires; concerning the knowledge; concerning the progeny; concerning self. these are called great sanhitas. 

now concerning the worlds. prithvi is first form, dyaw is second form; aakash is the linking, vaayu is joint of linking, 
next concerning the shining fires. agni is first form, aaditya is second form, aapah is linking, vidyut is joint of linking. 
next concerning the knowledge. master is first form, disciple is second form, knowledge is the linking, exposition is joint of linking. 
next concerning progeny. the mother is the first form, father is second form, progeny is linking, act of procreation is joint of linking. 
next concerning self. upper jaw is first form, lower jaw is second form, speech is linking, tongue is joint of linking. 
these are the great samhitas. he who know thus the great samhitas as we have expounded them, to him are linked progeny, radiance of holiness, and world of his high estate in heaven.