denotes purity, simplicity, and candour; innocence, truth, and hope. The ancient Druids, and indeed the priests generally of antiquity, used to wear white vestments, as do the clergy of the Established Church of England when they officiate in any sacred service. The magi also wore white robes.
The head of Osiris, in Egypt, was adorned with a white tiara; all her ornaments were white; and her priests were clad in white.
The priests of Jupiter, and the Flamen Dialis of Rome, were clothed in white, and wore white hats. The victims offered to Jupiter were white. The Roman festivals were marked with white chalk, and at the death of a Caesar the national mourning was white; white horses were sacrificed to the sun, white oxen were selected for sacrifice by the Druids, and white elephants are held sacred in Siam.
The Persians affirm that the divinities are habited in white.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894