The Heptameron of Peter of Abano was written by the Italian philosopher Pietro of Abano observer and astrologer who died in prison during the Inquisition in allegations of heresy and atheism. He lived from 1250-1316, but his work, the Heptameron was not published until the end of 1400. The text is a manual on planetary magic. It details the rites to summon the angels for each of the seven days of the week. It also contains instructions for creating the magic circles, the consecrations of salt, water, and frankincense, and planetary hours. This grimoire was especially important, since it influenced the Lemegeton, a famous book of the 17 th century demonology.