German scholar and folklorist Wilhelm Mannhardt holds that the log represented an incarnation of the spirit of vegetation. The sacrifices offered to the "badnjak" were meant to guarantee the fertility of fields, the health and happiness of the family. Its burning symbolized sunshine, and was intended to secure the vitalizing power of the sun in the ensuing year. The lighting of the log could be regarded as a fusion of tree worship and fire worship, attested in Slavic customs; e.g., Istrians fed the logs lighted on St. John's Day by sprinkling wheat upon them. Čajkanović characterizes the pre-Christian "badnjak" as a divinity who dies by burning to be reborn, comparing it in this respect with Attis, Osiris, Adonis, and Sandan. He also proposes that the crosses made from the thicker end of the log may have originated from idols representing deities comparable with the Roman Lares, the cruciform having developed from an anthropomorphic shape of the idols. The "badnjak" is preferably cut from an oak, which was the most respected tree in the old Slavic religion, associated with the supreme god Perun.