When I was hard at work one day, thinking on the spiritual work needful for God's servants, four such spiritual works came to my mind, these being: reading; meditation; prayer; contemplation. This is the ladder for those in cloisters, and for others in the world who are God's Lovers, by means of which they can climb from earth to heaven. It is a marvellously tall ladder, but with just four rungs, the one end standing on the ground, the other thrilling into the clouds and showing the climber heavenly secrets.

Guigo II, A Laddere of Foure Ronges (1150)