On top of page 17 of The Teaching of Buddha is a quote that sounds very much like the Four Great Vows; even allowing for the paraphrasing in this book. The source is given as the mahayana-jataka-cittabhumi-pariksa-sutra. Anyone seen an english translation of this work?
Or maybe someone knowing it could confirm or disprove this passage being in this sutra. It begins: "When Buddha decided to break from the worldly life, he made four great vows..."