The Deeper Symbolism of Freemasonry from The Meaning of Masonry by Walter Leslie Wilmshurst.

“We are told seven or more years was the normal period, though less sufficed in worthy cases. The most severe tests of discipline, of purity, of self-balance were required before a neophyte was permitted to pass forward, and a reminiscence of these tests of fitness is preserved in our own working by the conducting of the candidate to the two wardens, and submitting him to a merely formal trial of efficiency.” [via]