The title. Tehuti, or Thoth, is the Egyptian god of wisdom, knowledge, and magick; the Greeks identified him with Hermes. In Egyptian mythology, Thoth often played the part of diplomat, healed rifts between quarreling gods, or kept the peace. In some stories, he brought forth the universe through the power of his voice.
(line 1) "They do homage to him as he cometh forth," etc. From plate 26 of The Egyptian Book of the Dead (E.A. Wallis Budge translation).
(line 6)"Get thee back to the heights of heaven." Same. The full quote is, "The double Lion-god, the warder of the things that belong to the house of the nemmes crown which is in his hiding place, saith unto me: 'Get thee back to the heights of heaven, seeing that through Horus thou hast become glorified in thy form; the nemmes crown is not for thee; thou hast speech even unto the ends of heaven.'"
(lines 10-11) "When shall I come to th' top of that same hill?", etc. From Shakespeare's King Lear; the first two lines of Act 4, Scene 6 (Gloucester, then Edgar). Edgar is leading his blinded father Gloucester through the southeastern English countryside near Dover, disguised as a peasant, pretending to help Gloucester kill himself by jumping off the Dover cliffs while actually having no intention of letting that happen.
(line 12) Excelsior. Latin for "Ever higher."
(line 15) Logos The Divine Word (Greek, literally meaning "word").
(line 16) We stand last in line, etc. A paraphrase of a line from Dio's song "The Last In Line."
(line 17) Be wise as serpents. The Bible, Matthew 10:16 (an alleged statement of Jesus to his disciples): "Behold, I send you forth as sheep in the midst of wolves: be ye therefore wise as serpents, and harmless as doves." (King James Version)
(line 18) Satan casts out Satan. Same, Matthew 12:26 (again, an alleged statement of Jesus): "And if Satan cast out Satan, he is divided against himself; how shall then his kingdom stand?" (King James Version)
(lines 21-24) "Why should a dog," etc.King Lear, Act 5, Scene 3 (the final scene; Lear). Lear is mumbling over the corpse of his murdered daughter Cordelia just before he collapses and dies of heart failure.