Major Arcana · Key 19
The Sun
Read to know yourself, not to surrender yourself: relate to the card; never obey it. These are what two traditions wrote, not predictions.
In Waite's words: The Pictorial Key to the Tarot (1911)
The naked child mounted on a white horse and displaying a red standard has been mentioned already as the better symbolism connected with this card. It is the destiny of the Supernatural East and the great and holy light which goes before the endless procession of humanity, coming out from the walled garden of the sensitive life and passing on the journey home. The card signifies, therefore, the transit from the manifest light of this world, represented by the glorious sun of earth, to the light of the world to come, which goes before aspiration and is typified by the heart of a child.
But the last allusion is again the key to a different form or aspect of the symbolism. The sun is that of consciousness in the spirit - the direct as the antithesis of the reflected light. The characteristic type of humanity has become a little child therein— a child in the sense of simplicity and innocence in the sense of wisdom. In that simplicity, he bears the seal of Nature and of Art; in that innocence, he signifies the restored world. When the self-knowing spirit has dawned in the consciousness above the natural mind, that mind in its renewal leads forth the animal nature in a state of perfect conformity.
The upright and reversed meanings above are from Waite's own list of the trumps' divinatory meanings, Part III §3 of the same book; see them all, with his Celtic Cross, on Tarot spreads.
A. E. Waite, The Pictorial Key to the Tarot (London: William Rider & Son, 1911), public domain.
In the Golden Dawn's Book T (1912)
The Lord of the Fire of the World
Glory, gain, riches. With "very" evil cards it means arrogance, display, vanity.
Correspondences
Hebrew letter: ר (Resh, 'head') — path 30 on the Tree of Life.
On the Tree: path 30 joins Hod and Yesod · see it on the map
Attribution: the Sun.
(Classical Golden Dawn / Book T attribution. Modern decks add an outer planet — Uranus, Neptune, or Pluto — to the three elemental trumps.)
Astrological attribution (Book T)
Book T as printed in The Equinox I(8), 1912, public domain (notes in square brackets are Crowley's). The correspondences are this site's compilation from Book T. Open it in the Golden Dawn deck.