Upanishad carries the sense of sitting near a teacher, and these texts turn from the rite toward the questions behind it — what the self is, and what it is that does not change. They stand at the close of each Veda and are known for that reason as Vedanta. Thirteen are commonly treated as principal, while the Muktika Upanishad names a list of one hundred and eight.
'Satyameva Jayate' on India's national emblem is not a modern slogan. It is half a line from the Mundaka Upanishad, 3.1.6.
Source: Mundaka Upanishad 3.1.6Isha Upanishad ईशावास्योपनिषद्
The Isha Upanishad belongs to the Shukla Yajurveda and runs to eighteen verses. It opens with the line that all this is pervaded by the Lord, and moves from there to how a person may act and live within that understanding. Its brevity has made it a common place to begin among the principal Upanishads.
Katha Upanishad कठोपनिषद्
The Katha Upanishad tells of the boy Nachiketa, who comes to the house of Yama and asks what remains when a person dies. Yama offers him wealth and long years in place of an answer, and Nachiketa sets them aside. The dialogue that follows gives the image of the Self as the rider, the body as the chariot, the intellect as its charioteer, the mind as the reins, and the senses as the horses.
Mandukya Upanishad माण्डूक्योपनिषद्
The Mandukya Upanishad is set out in twelve verses and takes the syllable Om as its subject. It reads the three sounds of Om as the waking, dreaming, and deep-sleep states, and the silence that follows them as turiya, the fourth. Sage Gaudapada's Karika is the commentary traditionally read alongside it.
Chandogya Upanishad छान्दोग्योपनिषद्
The Chandogya Upanishad belongs to the Samaveda, and in it Rishi Uddalaka instructs his son Shvetaketu through images drawn from ordinary things — a seed opened, salt dissolved in water — each returning to the same recognition. The instruction closes with the sentence the tradition carries as tat tvam asi. Its earlier chapters take up the udgitha and the syllable Om.
Brihadaranyaka Upanishad बृहदारण्यकोपनिषद्
The Brihadaranyaka Upanishad belongs to the Shukla Yajurveda and is attached to the Shatapatha Brahmana. It carries the dialogues of Rishi Yajnavalkya, including his exchange with Maitreyi on what is worth desiring, and his answers in the assembly of King Janaka. The prayer asking to be led from the unreal to the real, and from darkness to light, is found here.