In Kashmir Sahaivist teaching, only 6 of the 8 limbs are given importance;
From: http://www.universalshaivafellowship.com/usf/teachings_04.html#Discipline
In his translation of the 4th chapter of Tantraloka, Swami Lakshmanjoo explains that Abhinavagupta has given importance to only six limbs of yoga–pranayama, pratyahara, dhyana, dharana, tarka and samadhi. Swamiji points out that the eight limbs of yoga, set out by Patanjali, help those aspirants residing on the lower level of practice, the means known as anavopaya. But for more advanced practice, the means known as shaktopaya and shambhavopaya, they are of no use. The main point in Kashmir Shaivism is “awareness.”

In Trika Shaivism pranayama, pratyahara, dhyana and dharana are considered to be external ways of maintaining the strength of yoga. There is only one predominant limb of yoga that is “tarka.” Tarka means ‘perception which differentiates'. It is discriminating, transcendental logic. This fifth limb of yoga is the discrimination between individual and universal, i.e. discriminating logic and reasoning from within your own consciousness.

Though the first three limbs of ashtanga yoga (yama, niyama and asana) are not mentioned in Kashmir Shaivism, Swamiji gave great importance to the yama of Ahimsa (non-violence) and the niyama of Ishvara Pranidana (devotion to Lord Shiva).
(There is more on the page)

similarly
From: http://www.crystalinks.com/yoga.html
In the Maitrayaniya Upanishad (ca. 200-300 BCE) yoga surfaces as:"Shadanga-Yoga - The uniting discipline of the six limbs (shad-anga), as expounded in the Maitrayaniya-Upanishad: (1) breath control (pranayama), (2) sensory inhibition (pratyahara), (3) meditation (dhyana), (4) concentration (dharana), (5) examination (tarka), and (6) ecstasy (samadhi).