Innocently reading through an introduction to European mysticism* I found a strange person mentioned, Wilhelmine von Böhmen. In the chapter about Italian mystics the usual suspects are listed like Dante, Francisus, Angela da Foligno (Ger., Eng.), Katharina da Siena (Ger., Eng.; book) et al. In the last paragraph Guglielma (Vilemina, Wilhelmine) Bohemica is called a stigmatised. The list of catholic stigmatised people is pretty long I guess, but I have never heard about a Bohemian Wilhelmina.
As WEHR says she appeared in Milano (Ger., Eng.) around/after 1260, formed a group of followers, and died there 1279 (according to wikipedia 1281). The group believed that the holy ghost was embodied in Wilhelmina, and that the new æra of the renovated ecclesia spiritualis (what would start according to Joachim von Fiore (Ger., Eng.) in the year 1260) would be dominated by the charismatic woman, she’d be the new pope.
The body of source material is very thin, it seems to be only one report: The Carthusian monk Matteo VALERIANO (I could find nothing about him) went into a grocer’s store (Where? When?) “in the 16th century” and noticed that the goods were wrapped in sheets of written pergamentum. He bought the “wrapping paper”. It was the file on the process of the Wilhelminiten by the notarius Beltramus SALVAGNIUS (no further info), sadly not complete. There must have been another report, the second notarius was Manfredo da CERA (no further info), but it is seemingly lost. The wikipedia-article mentions that “in 1788 the archive in Milano burnt down”, but I do not know what archive is meant, and could not verify this.
Wilhelmina** was the daughter of king Ottokar I. Premysl (Ger., Eng.) from Bohemia and his second wife Constance from Hungaria (Ger., Eng.). She was born 1210 and died on the 24th of August 1281 in Milano. She was first buried in the cemetery of San Pietro all’Orto, later her body was brought into the abbey of Chiaravalle (Ger., Eng.). Her successor was Mayfreda PIROVANO of the cloister in Biassono (Ger., Eng.).
The idea was that the renovatio of the church, the already mentioned start of the new æra, would be led and dominated by females and that the holy spirit was embodied in Wlhelmina. Her successor Mayfreda acted as pope to their adherents and they formed not only a loose group, but a real sect. Mayfreda teached, preached, and administered the sacraments. Her followers called her in letters “dominus meus dominus vicarius”, a formula reserved for the pope, they also kissed her foot and hand. In 1284 the inquisition took notice of the group, some members were interrogated; they renunciated their errors, received a symbolic punishment and that was that.
In 1296 pope Bonifacius VIII. (Ger., Eng.) signed the bulla S[a]epe Sanctam Ecclesiam (aka Nuper ad Audientiam***), where in the first part practices were described as heretic that the Guglielmites seemingly had accepted: Women preaching, solving and binding, hearing confession, giving absolution, wearing the tonsur (Ger., Eng.). The final blow came 1300. Mayfreda held the Easter liturgy on the 10th of April. She was called before the inquisition on the 19th; a new process started on the 20th of July, and in September Mayfreda, together with Jacoba BASSANI, Bellacara CARENTANO, Andreas SARAMITA, and the remains of Wilhelmina, was burnt to death. The rest of the group survived.
Sister Mayfreda belongs to the important Milanese VISCONTI family, cousin of a Matteo VISCONTI, and interestingly a Galeazzo VISCONTI is among the members of the heretic group. Whether there is a connection to “Aradia di Toscano” (Ger., Eng.) is imho at least doubtful.
* WEHR, Gerhard: Europäische Mystik zur Einführung, Hamburg 1995 (Zur Einführung 121)
** I follow the German wikipedia article.
*** I cite this bulla following the aformentioned wikipedia-article, but am unable to verify this: I have not found such a bulla. Maybe it is another papal instrumentum; if anyone can shed some light on this, I’d be very happy to complement this!