Here is Where Clement Got His Idea for the 'Truth that Is Hidden By Seven Veils'

P Alexander Mystical Texts: the Song of the Sabbath Sacrifice and related texts (New York, Continuum, 2006) p 36, 37 “The celestial curtain was a subject of extensive speculation in later mystical texts (Hofius 1972) ...The veil is also pluralized, for while4Q405 15 ii-16 3 speaks of 'the veil of the debir of the King' in the singular, two lines later we have a reference to 'the veils of the wondrous debirim’ in the plural. If there are seven debirs,then, logically, there must be seven veils. It is probable that the description of the celestial veil was followed by a description of God's heavenly throne, which would have stood behind the veil ... The mention of ‘eternal thrones’ (kis’ei ‘olamim) in the previous line is important. The reference must be to God's throne ... The throne, like the curtain, may have been depicted as engraved with figures of angels which praise and bless God. The idea of God's throne ties in with the royal imagery of the Songs. The commonest title for God in Sabbath Songs is 'the King'”