Amulets are frequently mentioned in talmudic literature. The term used is kame'a or kami'a (pl. kemi'ot or kemi'in), a word whose origin is obscure. The written kame'a was a parchment inscribed with one or more quotations from a variety of sources, including the Scriptures (cf. Shab. 61b). Later amulets were inscribed with quotations relevant to their specific purpose. The text of the Priestly Blessing (Num. 6:24–26) was considered effective against the "evil eye." Permutations and combinations of the letters of the different names of G-d were frequently used; names of angels were also very common. Amulets subsequently merged with the Kabbalah and came to be known as "practical Kabbalah." Many mystical texts, such as the Sefer Yezirah and the Sefer Razi'el, contain instructions for the preparation of amulets and other charms, for a variety of purposes.