CC Ādi 7.108

upaniṣat-sahita sūtra kahe yei tattva
mukhya-vṛttye sei artha parama mahattva
Synonyms: 
upaniṣat — the authorized Vedic version; sahita — along with; sūtra — the Vedānta-sūtra; kahe — it is said; yei — the subject matter; tattva — in truth; mukhya-vṛttye — by direct understanding; sei — that truth; artha — meaning; parama — ultimate; mahattva — glory.
Translation: 
“The Absolute Truth is described in the Upaniṣads and Brahma-sūtra, but one must understand the verses as they are. That is the supreme glory in understanding.
Purport: 

It has become fashionable since the time of Śaṅkarācārya to explain everything regarding the śāstras in an indirect way. Scholars take pride in explaining everything in their own way, and they declare that one can understand the Vedic scriptures in any way he likes. This “any way you like” method is foolishness, and it has created havoc in the Vedic culture. One cannot accept scientific knowledge in his own whimsical way. In the science of mathematics, for example, two plus two equals four, and one cannot make it equal three or five. Yet although it is not possible to alter real knowledge, people have taken to the fashion of understanding Vedic knowledge in any way they like. It is for this reason that we have presented Bhagavad-gītā As It Is. We do not create meanings by concoction. Sometimes commentators say that the word kurukṣetra in the first verse of the Bhagavad-gītā refers to one’s body, but we do not accept this. We understand that Kurukṣetra is a place that still exists, and according to the Vedic version it is a dharma-kṣetra, or a place of pilgrimage. People still go there to perform Vedic sacrifices. Foolish commentators, however, say that kurukṣetra means the body and that pañca-pāṇḍava refers to the five senses. In this way they distort the meaning, and people are misled. Here Śrī Caitanya Mahāprabhu confirms that all Vedic literatures, including the Upaniṣads, Brahma-sūtra and others, whether śruti, smṛti or nyāya, must be understood according to their original statements. To describe the direct meaning of the Vedic literatures is glorious, but to describe them in one’s own way, using imperfect senses and imperfect knowledge, is a disastrous blunder. Śrī Caitanya Mahāprabhu fully deprecated the attempt to describe the Vedas in this way.

Regarding the Upaniṣads, the following eleven Upaniṣads are considered to be the topmost: Īśa, Kena, Kaṭha, Praśna, Muṇḍaka, Māṇḍūkya, Taittirīya, Aitareya, Chāndogya, Bṛhad-āraṇyaka and Śvetāśvatara. However, in the Muktikopaniṣad, verses 30-39, there is a description of 108 Upaniṣads. They are as follows: (1) Īśopaniṣad, (2) Kenopaniṣad, (3) Kaṭhopaniṣad, (4) Praśnopaniṣad, (5) Muṇḍako-paniṣad, (6) Māṇḍūkyopaniṣad, (7) Taittirīyopaniṣad, (8) Aitareyo-paniṣad, (9) Chāndogyopaniṣad, (10) Bṛhad-āraṇyakopaniṣad, (11) Brahmopaniṣad, (12) Kaivalyopaniṣad, (13) Jābālopaniṣad, (14) Śvetāś-vataropaniṣad,(15) Haṁsopaniṣad, (16) Āruṇeyopaniṣad, (17) Garbho-paniṣad, (18)  Nārāyaṇopaniṣad, (19) Paramahaṁsopaniṣad, (20) Amṛta-bindūpaniṣad, (21) Nāda-bindūpaniṣad, (22) Śiropaniṣad, (23) Atharva-śikhopaniṣad, (24) Maitrāyaṇy-upaniṣad, (25) Kauṣītaky-upaniṣad, (26) Bṛhaj-jābālopaniṣad, (27) Nṛsiṁha-tāpanīyopaniṣad, (28) Kālāgni-rudropaniṣad, (29) Maitreyy-upaniṣad, (30) Subālopaniṣad, (31) Kṣuri-kopaniṣad, (32) Mantrikopaniṣad, (33) Sarva-sāropaniṣad, (34) Nirā-lambopaniṣad, (35)Śuka-rahasyopaniṣad, (36)Vajra-sūcikopaniṣad, (37) Tejo-bindūpaniṣad, (38) Nāda-bindūpaniṣad, (39) Dhyānabindū-paniṣad, (40)Brahma-vidyopaniṣad, (41)Yoga-tattvopaniṣad, (42) Ātma-bodhopaniṣad, (43) Nārada-parivrājakopaniṣad, (44) Triśikhy-upaniṣad, (45) Sītopaniṣad, (46) Yoga-cūḍāmaṇy-upaniṣad, (47) Nirvāṇopaniṣad, (48) Maṇḍala-brāhmaṇopaniṣad, (49) Dakṣiṇā-mūrty-upaniṣad, (50) Śarabhopaniṣad, (51) Skandopaniṣad, (52) Mahānārāyaṇopaniṣad, (53) Advaya-tārakopaniṣad, (54) Rāma-rahasyopaniṣad, (55) Rāma-tāpaṇy-upaniṣad, (56) Vāsudevopaniṣad, (57)Mudgalopaniṣad, (58)Śāṇḍilyopaniṣad, (59)Paiṅgalopaniṣad, (60) Bhikṣūpaniṣad, (61) Mahad-upaniṣad, (62) Śārīrakopaniṣad, (63) Yoga-śikhopaniṣad, (64) Turīyātītopaniṣad, (65) Sannyāsopaniṣad, (66) Paramahaṁsa-parivrājakopaniṣad, (67) Mālikopaniṣad, (68) Avyaktopaniṣad, (69) Ekākṣaropaniṣad, (70) Pūrṇopaniṣad, (71) Sūryopaniṣad, (72) Akṣy-upaniṣad, (73) Adhyātmopaniṣad, (74)  Kuṇḍikopaniṣad, (75) Sāvitry-upaniṣad, (76) Ātmopaniṣad, (77) Pāśupatopaniṣad, (78) Param-brahmopaniṣad, (79)  Avadhūtopaniṣad, (80) Tripurā-tapanopaniṣad, (81) Devy-upaniṣad, (82) Tripuropaniṣad, (83) Kaṭha-rudropaniṣad, (84) Bhāvanopaniṣad, (85) Hṛdayopaniṣad, (86) Yoga-kuṇḍaliny-upaniṣad, (87) Bhasmopaniṣad, (88) Rudrākṣo-paniṣad, (89) Gaṇopaniṣad, (90) Darśanopaniṣad, (91) Tāra-sāropaniṣad, (92) Mahā-vākyopaniṣad, (93) Pañca-brahmopaniṣad, (94) Prāṇāgni-hotropaniṣad, (95) Gopāla-tāpany-upaniṣad, (96) Kṛṣṇopaniṣad, (97) Yājñavalkyopaniṣad, (98) Varāhopaniṣad, (99) Śāṭyāyany-upaniṣad, (100) Hayagrīvopaniṣad, (101) Dattātreyopaniṣad, (102) Gāruḍopaniṣad, (103) Kaly-upaniṣad, (104) Jābāly-upaniṣad, (105) Saubhāgyopaniṣad, (106) Sarasvatī-rahasyopaniṣad, (107) Bahvṛcopaniṣad and (108) Mukti-kopaniṣad. Thus there are 108 generally accepted Upaniṣads, of which eleven are the most important, as previously stated.