Vnislav was the fourth of the seven Bohemian mythical princes between the (also mythical) founder of the P?emyslid dynasty P?emysl the Ploughman and the first historical prince Bo?ivoj. The names of the princes were first recorded in Cosmas chronicle and then transmitted into the most of historical books of the 19th century including Franti?ek Palacký's The History of the Czech Nation in Bohemia and Moravia.
One theory about the number of the princes is propped on the frescoes on the walls of the Rotunda in Znojmo, Moravia but Ane?ka Merhautová claimed that the frescoes depict all the members of the P?emyslid dynasty including the Moravian junior princes.
Vnislav's name is a typical Slavonic name ending in -slav (such as Wenceslas, Vladislav, Vít?zslav etc.) but there is confusion about the first part. Závi? Kalandra thought the names of the seven princes were cryptical names of ancient Slavonic days of the week - Vnislav being the fourth - Wednesday, in Latin dies Mercurii whereas Vnislav could refer to a Slavonic god of profit. Another theory says that the names were mistaken from a coherent and partly interrupted old Slavonic text.