I was asked where the phrase ‘on cloud nine’, which means to be in a state of blissful happiness, originates from. So I’ve started a new category called “idiomatic expressions” and this is the first entry. This was sourced from:
The usual explanation of its origin is that it comes from the US Weather Bureau.The story is that this organisation describes (or once described) clouds by an arithmetic sequence. Level Nine was the very highest cumulonimbus, which can reach 30,000 or 40,000 feet and appear as glorious white mountains in the sky. So if you were on cloud nine you were at the very peak of existence.
However, according to Thomas Veil on the Phrase Finder website:
The true and original origin of “Cloud 9” is derived from Buddhism.
The state of being in “Cloud 9” is the penultimate goal of the Bhodisattva.
Check on Martin Luther King’s paper on
“The Chief Characteristics and Doctrines of Mahayana Buddhism”.
“The Mahavastu, a late Hinayana work, gives a list of ten stages in the progress of the Bodhisattva, and the same number is retained, with modifications in detail, by the Mahayana authorities… In the ninth stage the seeker reaches the point when all his acts are unselfish, done without desire. Finally the Bodhisattva reaches the tenth stage in which he becomes a tathagata, a cloud of dharma.[Footnote: Radhakrishnan, op. cit., pp. 601, 602.]
I believe that the ninth cloud is also referred to as “The Bright Cloud of Great Refuge”.
Finally, we have Christi the Wordsmith, who weighs in with:
In Dante’s Paradise, the 9th level of heaven is closest to the Divine Presence, which itself dwells at the 10th and highest heaven. This notion may have enhanced the popularity of the expression on cloud nine.
Sources:
http://www.phrases.org.uk/bulletin_board/18/messages/721.html
http://www.wordsmithradio.org/scripts/cloudnine.html
robertdesenior 
thank you
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