The poetic use of crystal has its basis in ancient mystical philosophy, which is partly noticed in the section under CRYSTAL. DIAMOND Shakespeare alludes to the diamond twenty-one times, most of all in “Cymbeline.” Imogen gives Posthumus as a pledge of affection her diamond ring: “_This diamond was my mother’s: take it, heart._” The diamond is mentioned four times as an important part of the plot in the bargain between Posthumus and Iachimo: “_If she went before others I have seen, as that diamond outlustres many I have beheld, I could not but believe that she excelled many: but I have not seen the most precious diamond that is, nor you the lady._” POSTHUMUS: “_I praised her as I rated her: so do I my stone._” “_I shall but lend my diamond till you return._” IACHIMO: “_My ten thousand ducats are yours: so is your diamond too: if I come off._” In Act 2, Scene 4, poor Posthumus says: “_All is well yet, Sparkles this stone as it was wont?_” alluding to the ancient belief that the diamond turned dull when lovers proved unfaithful. “_... The stone’s too hard to come by._” IACHIMO: “_I beg but leave to air this jewel: see! it must be married To that your diamond._” In Act 5, Scene 5, Cymbeline asks Iachimo: “_That diamond upon your finger—say, How came it yours?_” The diamond is mentioned three times in Pericles: MAISA: “_To me he seems like diamond to glass._” (Act II, Sc. 3.) HELICANUS: “_Whom if you find, and win unto return, You shall like diamonds sit about his crown._” CERIMON: “_She is alive: behold Her eyelids, cases to those heavenly jewels Which Pericles hath lost, Begin to part their fringes of bright gold: The diamonds of a most praised water Do appear, to make the world twice rich._” The diamond is mentioned three times in King Henry VI: “To me he seems like diamond to glass.” Pericles, Act II, Sc. 3. SUFFOLK: “_So farewell Reignier: set this diamond safe In golden palaces, as it becomes._” (Part 1, Act V, Sc. 8.) THE QUEEN: “_I took a costly jewel from my neck, A heart it was, bound in with diamonds, And threw it towards thy land._” (Part 2, Act III, Sc. 2.) [Illustration: HOROSCOPE OF SHAKESPEARE ] KING HENRY: “_My crown is in my heart not on my head: Not decked with diamonds and Indian stones Nor to be seen: my crown is called content A crown it is that seldom kings enjoy._” (Part 3, Act III, Sc. 1.) In the “Comedy of Errors,” the diamond is twice mentioned: