سيفر حباهر 96

1And corresponding to her (the earth) is the deep-blue/t’cheilet of the tsitsit (the corner fringes on a prayer shawl). For R’ Meir said: How is t’cheilet different from all kinds of colors? Because t’cheilet resembles the sea and the sea resembles the firmament and the firmament resembles the throne of glory, as it is said, “And they saw Israel’s God and under His feet [was something] like sapphire brick-work and like the essence of the heavens for purity” [Ex 24:10] and it says, “like the appearance/mar’eh of sapphire stone, a likeness of a throne / d’mut kisei’” [Ez 1:26].