Longdé

[2] According to Sten Anspal this class of texts "is difficult to define or characterize uniformly" and "were not unified into a single system".

encompassing everything: it is devoid of characteristics and cannot be apprehended; it is without center or periphery; it is eternal and uncaused; there is no support in space and nothing to focus on: and so forth.

[3] As noted by Anspal, some Space Series tantras like Equal to the End of Sky (Nam-mkha'i mtha'-dang mnyam-pa) "do not prescribe any particular techniques for the practitioner, such as physical postures or movements, structured meditative exercises, etc."

[3]In the Vajra Bridge tradition, contemplation of the true nature of mind, which was also referred to as "non-meditation", was introduced through the use of "four signs", which "are the experiences of non-conceptuality (mi-rtog-pa), clarity (gsal-ba), bliss (bde-ba) and the inseparability (dbyer mi-phyed-pa) of the first three as the fourth.

"[3] Some of the Vajra Bridge texts also make use of subtle body yogas of winds (vayus), though they are relatively simple and "effortless" (rtsol-bral) in comparison to the wind yogas of the completion stage found in the Sarma tantras, which are seen as inferior and coarse by the Vajra Bridge authors such as Kun-bzang rdo-rje.

[6] Additionally, there is one terma text in the Space Class, which is contained in the Chokling Tersar cycle of Orgyen Chokgyur Lingpa.

[7] Tulku Urgyen writes, no other terton has revealed a teaching that includes the Space Section (Longde) of Dzogchen.