Is a Mesorah (direct tradition) required for the identification of the ?חלזון

As with almost every area of Halacha, a Mesorah is not required for the identification of the חלזון . Even in areas of Halacha where it is necessary to determine the definition of a specific term, object or animal, a Mesorah is not required. Any reliable source can be used for
determining facts 136, even when they relate to Halacha 137.

• Regarding the identity of the non-kosher birds mentioned in
  the Torah, the Ramban and other Rishonim identify the birds
  based on the signs of the Gemara as well as his personal
  inspection of the birds and their anatomy138.
• Similarly, regarding the Shekel of the Torah (- Halachically relevant for Pidyon Haben), the Ramban determined its value based on an ancient coin that was shown to him when he arrived in Eretz Yisrael 139.
• The Rishonim dispute the identity of אורז , whether it is rice or millet regarding which one requires 140 ברכת מזונות . The Gr”a is well known to have determined the identity of אורז as rice, by experimentation alone 141.

Regarding תכלת itself, the Maharil (1360-1427 CE) writes that it can be restored purely using the signs describing the :חלזון

שו”ת מהרי”ל החדשות )סימן ה ד”ה ב(: “… וסברא הוא דשמא יחזור דבר לקילקולו שיהא תכלת מצוי, כ”ש למאי דכתב סמ”ג )עשה כ”ו( דאותו דג חלזון הוא בים המלח וכתב סימנין, בקל היה לעשות תכלת…”.

“Thus it is logical, for perhaps there will again be a problem that תכלת will be found [and תכלת which is wool would involve a Shaatnez issue]. Certainly according to what the Smag wrote, that the חלזון is found in the salty sea [- Mediterranean 142] and he gave signs [to identify it], it would
be simple to create ”…תכלת

In the same vein, the בית הלוי stated that if it is proven that the חלזון has been found (even without a direct tradition); we would be obligated to wear it:

“כמע”ל לא ביאר בדבריו מה זאת מצא אחר שנשכח, אם מציאת הדג או הוצאת צבעו, ורק אחרי אשר כמע”ל יברר זאת, היינו היה
בזה דבר הנשכח והוא מצאה, אז נהיה מחויבים לשמוע אליו . וללבשו” 143

“His Honor has not explained what is it that he has found after it has been forgotten, is it the discovery of the fish or the method of extracting the dye. Only after His Honor will clarify this – that it is something forgotten that he has found – then we will be obligated to listen to
him and don it.”

Other Acharonim also state that תכלת can return at any point in
history, without necessitating a Mesora 168.

Bottom Line: A Mesorah is not required to establish a Halachic practice, if it can be sufficiently proven by other means.

R’ Hershel Schachter addresses his Mesorah issue as follows. Among the Gedolim, there was an epic correspondence between a letter from a friend of the Beis Halevi, R’ Yosef Dov Soloveitchik (Skutzk/Brisker Rav in the 1800’s) and R’ Gershon Henoch Leiner, of which the former roundly rejected the Radzyn Techeiles attempt based on the cuttlefish Chilazon found. There are two versions.

The Soloveitchik version is that one must have a Mesorah and you can’t reinstate things by archeological evidence or by visiting an aquarium and try to figure based on Simanim. He gave an example of Orez versus Dochen and which one has the bracha of Mezonos versus HaAdama. While Orez/Arroz is defined as rice in Arabic as well as Spanish, his retort was that one couldn’t rely on a “lexicon” (dictionary) for the definition, but one needed a Mesorah.

The Radzyn version was more nuanced: R’ Soloveitchik replied that our parents and grandparents knew about this squidfish that spits out the black dye, since it was commonly used for ink at the time. If they knew about this Chilazon and chose not to use it for Techeiles, then it actually counts as a negative Mesorah. However, if one can show him a new fish not known to our parents and grandparents, and a good reason for the disuse of this creature for Techeiles and why now is different, he would be the first one on board.

R’ Feivel Cohen spent a year with R’ Yosef Shalom Elyashiv to get shimush by him. After he returned to New York they corresponded frequently, and in one of the letters, he asked R’ Elyashiv which one of the two versions made sense. R’ Elyashiv’s response was that the Soloveitchik version made no sense, and that one can use Archeological evidence to reconstruct Mesorah. R’ Cohen then asked what he thought of the new Techeiles, and the response was “let me get back to you.” (He never did.)

R’ Schachter also points out that one person asked R’ Yosef Dov Soloveitchik about Mesorah based on the story of Rabba Bar Bar Chana, who went in the Midbar with a Taya (Arab tour guide) to see the Meisei Hamidbar. He returned to the Beis Medrash where there was a Machlokes between Beis Shammai and Beis Hillel on how many strings should go through each corner. He told them of his trip and they asked him, did you see how many strings the Meisei Midbar had? To which he replied that it didn’t occur to him to do so, at which point they called him an idiot for not doing so. That’s another example of using archeological evidence to reconstruct Mesorah.

Other examples of reconstructing Mesorah include:

1. R’ Eliezer seeing the golden Tzitz in Rome to see if it’s one or two lines (Shabbos 63b). The Rambam in response writes that the Tzitz can have one or two lines and both types were made.
2. the Ramban changing his opinion of the weight of a Shekel from the Rif to Rashi after Samaritans showed him a Shekel in Israel upon making Aliyah (see Ramban Shemos 30:13 and Ramban al HaChumash HaArah Be’Inyan HaShekel). Rashi’s weight is 1/6th lighter than the Rif’s opinion, which has potential implications on matters like Pidyon HaBen if the Rif was correct and Rashi was wrong.
3. Turkey consumption. Birds traditionally need a Mesorah, but the question is whether the 14 birds listed in the Gemara were the Ikkar or that they simply weren’t birds of prey. In practice turkey became a kosher bird even though we only knew about it relatively recently.
4. Teruma and Maaser after not being in Eretz Yisrael for a long time
5. And more.
6. One last point: R’ Belsky told R’ Eliyahu Ferrel of the OU that with solid Rayos, it’s “K’Ilu there is a Mesorah.”

Navon explains that the Murex trunculus was completely lost to Jewish knowledge for at least 900–1500 years. Halacha allows rediscovery of mitzvos through evidence if Mesorah was interrupted. The Beit HaLevi only rejected the Radzyner cuttlefish because it was a known creature without a tradition; this does not apply to the Murex, which was truly lost.
Source: “On History, Mesorah, and Nignaz,” pp. 18–24