Antisemitism in popular European Christian culture escalated beginning in the 13th century. Blood libels and host desecration drew popular attention and led to many cases of persecution against Jews. Many believed Jews poisoned wells to cause plagues. In the case of blood libel it was widely believed that the Jews would kill a child before Easter and needed Christian blood to bake matzo. Throughout history if a Christian child was murdered accusations of blood libel would arise no matter how small the Jewish population. The Church often added to the fire by portraying the dead child as a martyr who had been tortured and child had powers like Jesus was believed to. Sometimes the children were even made into Saints. Antisemitic imagery such as Judensau and Ecclesia et Synagoga recurred in Christian art and architecture. Anti-Jewish Easter holiday customs such as the Burning of Judas continue to present time. In Iceland, one of the hymns repeated in the days leading up to Easter includes the lines,  During the Middle Ages in Europe persecutions and formal expulsions of Jews were liable to occur at intervals, although it should be said that this was also the case for other minority communities, regardless of whether they were religious or ethnic. There were particular outbursts of riotous persecution during the Rhineland massacres of 1096 in Germany accompanying the lead-up to the First Crusade, many involving the crusaders as they travelled to the East. There were many local expulsions from cities by local rulers and city councils. In Germany the Holy Roman Emperor generally tried to restrain persecution, if only for economic reasons, but he was often unable to exert much influence. In the Edict of Expulsion, King Edward I expelled all the Jews from England in 1290 (only after ransoming some 3,000 among the most wealthy of them), on the accusation of usury and undermining loyalty to the dynasty. In 1306 there was a wave of persecution in France, and there were widespread Black Death Jewish persecutions as the Jews were blamed by many Christians for the plague, or spreading it. As late as 1519, the Imperial city of Regensburg took advantage of the recent death of Emperor Maximilian I to expel its 500 Jews. The largest expulsion of Jews followed the Reconquista or the reunification of Spain, and it preceded the expulsion of the Muslims who would not convert, in spite of the protection of their religious rights promised by the Treaty of Granada (1491). On 31 March 1492 Ferdinand II of Aragon and Isabella I of Castile, the rulers of Spain who financed Christopher Columbus' voyage to the New World just a few months later in 1492, declared that all Jews in their territories should either convert to Christianity or leave the country.