Source: TW
mayUrAsana
The mayUrAsana, where you hoist yourself on your posteriorly directed palms, was most likely invented by the vaikhAnasa-s. The urethral yoga-s of vajroli (bauddha vajrayANa) and amaroli (amaraugha-shAsana: shaiva successors of mIna) were probably derived from an ancestral version of this in the shaiva tradition.
khecharI
khecharI-mudra and at least two of the tri-bandha-s – jAlandhara and oDDiyAna – were canonized in the kaula tradition, most likely starting with the pUrvAmnAya (trika). Of course, khecharI has deep roots going back to the maitrAyaNIya shruti of the yajurveda itself, and a version of it close to the upaniShad was likely practiced by the tathAgata. But its integration into the mantramArga happens in the pUrvAmnAya as indicated by the khecharI-mudra tantra. It was subsequently also acquired by the pA~ncharAtrika vaiShNava-s.
The later haTha kuNDalinI practice was obviously derived from the pashchimAmnAya and dakShiNAmnAya, which themselves acquired it from their bhairavasrotas substratum (c.f., tantrasadbhAva), with deep roots in the veda itself. (when I say veda or shruti, I include the classical vedic upaniShad-s.)
mantra-mArga origins
This suggests that the practices of the later haTha traditions, like the dattAtreya saMhitA, were culled from various earlier mantra-mArga traditions, while underplaying their mantra component.
layayoga
layayoga appears to have again emerged from the bhairava-srotas. It is clear that the meditations of the laya tradition were derived from a tradition close to the vijnAnabhairava tantra, which was popular among the Kashmirian sAdhaka-s. We suspect that the Kashmirian vijnAnabhairava was originally attached to a larger tantra as its yoga section (= rudrayAmala? c.f. svachChanda-tantra).