The scale was originally ut re mi fa sol la si ut. It's from the initial syllables of the lines of a chant that I have on CD. The tones for each of the syllables go up scale. All I can remember off hand is

Ut queant laxis
Resonare fibris
Miserere nobis
Famili tuorum


but that might be filled with errors. I'll check tonight and give y'all the straight skinny.