"Baal HaTechelet"

The first to attempt, in practice, to identify the "chilazon" and restore the blue thread to tzitzit was Rabbi Gershon Chanoch Leiner - the 3rd Admor of the Izhbitz-Radzyn dynasty.

He wrote three books: "Sfunei Tmunei Chol," "Ptil Techelet," and "Ein HaTechelet" (the latter was published after the author's death), in which he, on the one hand, established the validity and necessity of seeking and restoring techelet, and on the other hand, identified the "chilazon" with the common cuttlefish (sepia officinalis).

He was far from the first to believe that the "chilazon" was the cuttlefish.