Ptil Tekhelet is the Radziner Rebbe (Rabbi Gershon Henoch Leiner)’s elaboration upon his treatise “Treasures Hidden in the Sand.” Ptil Tekhelet explains the Rebbe’s conclusion that the chilazon sea-creature described in rabbinic literature is the common cuttlefish, details the process of extracting the dye, and presents the laws of incorporating tekhelet into tzitzit (fringes affixed to four-cornered garments).