Saturday's vis wax combination for the "Rune Goldberg Machine" is:
1st. Slot: COSMIC rune (replace with AIR rune for 27/30)
2nd. Slot: Option A: FIRE rune (cheap enough so no replacement needed)
2nd. Slot: Option B: LAW rune (replace with MIND rune for 25/30)
2nd. Slot: Option C: NATURE rune (replace with CHAOS rune for 22/30)
3rd. Slot: random rune for every player
you may also go to runescape.wikia and look up "Rune_Goldberg_Machine" for the true cost of each rune