An extensive power over the principle of life was acquired by magic, chiefly sympathetic, prophylactic, or coercive, and it was possible to induce animal and vegetable fecundity, as by the sympathetic magic of the Midsummer fires.  Instances of the sacrifices of human life to ensure vegetable fecundity occur in the immolatin of the kings Domaldi and Oláfr (Ynglinga Saga, 18, 47); a slightly different case is that of Aunn, who gained an added ten years of life for each son sacrificed (ib. 29)... (Encyclopaedia of Religion and Ethics, Hastings, v.8, 1916).