Shimeon Cippah known in the Sefer Hasidim as Shimon Peter Chamor (פטר חמור) was a Tzadik according to the leader of Germany's twelfth century Hasidei Ashkenaz. Moreover, it is written in the Siddur Avodas Yisrael, in name of an old manuscript siddur from the year 1407:

“I heard from Yehuda Bar Yaakov that Shimon Ben Kipa authored Nishmas until the words Mi Yidmeh Lach”

Shimon also authored some Yom Kippur liturgy and others while in a cave according to the Machzor Vitri (p. 282 Mahadurah Makitzei Nirdamim) which also confirms his authorship of Nishmat and warns Vechas Veshalom to anyone who says anything about him as the "Abomination of Rome" and continues that anyone "who says so will have to bring a fat offering when Moshiach comes.” However, the Sefer Hasidim no.191, while admitting he was a Tzadik says it is necessary to call any tzadik by something disparaging if pagans take that tzadik as a deity.

The Teliya says he was the last leader of a Sanhedrin and later a Stylite some time after 224CE. He made an alliance with the Notzrim against Persian Judaizers who were attacking both Notzrut and Pavlut. He was instrumental in establishing the Miaphysite Church. He also sent all the Galilean compositions outside of the Jerusalem Talmud to the Exilarch in Babylon where the Babylonian Talmud was being composed.

The Machzor Vitri p. 282 Mahadurah Makitzei Nirdamim says

“Some say Nishmas was authored by an "Abomination of Rome" called Shimon Peter Chamor(!) -who authored this liturgy and others while in the cave- Vechas Veshalom to say such a thing (that Peter is an Abomination of Rome), and one who says so will have to bring a fat offering when Moshiach comes”

Vetzaruch Iyun (צריך עיון), as elsewhere in Machzor Vitri it states that Shimon Kipa authored the Piyutim of Seder Avoda said on Yom Kippur.

http://folkmasa.org/bet/bet001.htm

http://www.ybm.org.il/Admin/uploaddata/LessonsFiles/Pdf/4570.pdf

https://www.yutorah.org/_cdn/_shiurim/Fast%20of%20Ninth%20of%20Teves.pdf

http://chaimsimons.net/tevet9paper.pdf