Festivals involving processions were adopted by the Christian Church from the pagan calendar of Rome. The "litaniae majores et minores", which are stated by Hermann Usener to have been first instituted by Pope Liberius (352-366). It is generally acknowledged that they are the equivalent of the Christian Church of the Roman lustrations of the crops in spring, the Ambarvalia, &c. The "litania major", or great procession on St Mark's day (April 25) is shown to coincide both in date and ritual with the Roman Robigalia, which took place ad. vii. Kal. Mai., and consisted in a procession leaving Rome by the Flaminian gate, and proceeding by way of the Milvian bridge to a sanctuary at the 5th milestone of the Via Claudia, where the flamen quirinalis sacrificed a dog and a sheep to avert blight (robigo) from the crops. The litania major followed the same route as far as the Milvian bridge, when it turned off and returned to St Peter's, where mass was celebrated. This was already established as an annual festival by 598, as is shown by a document of Gregory the Great that inculcates the duty of celebrating litaniam, quae major ab omnibus appellatur. The "litaniae minores" or rogations, held on the three days preceding Ascension Day, were first introduced into Gaul by Bishop Mamertus of Vienne (c. 470), and made binding for all Gaul by the First Council of Orléans (511). The litaniae minores were also adopted for these three days in Rome by Pope Leo III (c. 800).