The Zodiac Killer seemed to draw inspiration from many sources of yesteryear, such as in the 408 Cipher, which contained the phrase "the most dangerous animal," believed to be referring to a short story 'The Most Dangerous Game' by Richard Connell, first published on January 19th 1924. The Mikado paraphrased in his Little List and Exorcist letters, first viewed by the paying public in 1885, and possibly Charlie Chan created by Earl Derr Biggers in 1919. His costumed appearance at Lake Berryessa and his use of words predominantly used by the British, made some people believe he may have been connected to the theater, in addition to being a well-read individual. The RCC library no doubt was well stocked and may likely have held the answer. This poem, apart from the very short Bates letters mailed on April 30th 1967, was effectively the preceding correspondence of any substance before the 408 cipher arrived in three parts to the San Francisco Chronicle, San Francisco Examiner and Vallejo Times-Herald - mailed on July 31st 1969, some 2 1/2 years later. So can any connection be forged?
Edward Hyde, Earl of Clarendon, Lord High Chancellor of England, was an English statesman and historian, with his writings detailed here in a catalog of English literary manuscripts containing one important section: "Naturally a substantial portion of Clarendon's surviving manuscripts comprises his personal correspondence — both letters received by him from numerous correspondents and his own letters, written or signed by him, whether drafts, retained copies, or the letters actually sent. Among many notable examples are his letters written in August 1646 to William, Lord Widdrington, and to Sir John Berkeley, announcing the beginnings of his History of the Rebellion, and the letter he wrote on 12 November 1646, to Sir Edward Nicholas, describing his plan for the work and stating that he had already completed sixty sheets of it. Some of his letters, particularly those dating from the Civil War period, are wholly or partly in cipher or make use of pseudonyms in both salutations and signatures. The codes to sixteen such ciphers used by the Royalists are written out in Bodleian, MS Clarendon 94, and see also British Library".
This is when I noticed another piece of obscure text from Edward, Earl of Clarendon and flew back to the last piece of notable text from the presumed Zodiac Killer on the Riverside desktop, the title of which was "sick of living/unwilling to die". One of Edward Hyde's quotes was “They who are most weary of life, and yet are most unwilling to die, are such who have lived to no purpose, — who have rather breathed than lived.” http://izquotes.com/quote/385232. Although not perfect, I couldn't help wondering if the Zodiac Killer was recalling from memory as he did with The Mikado, taking "weary of life, unwilling to die" to "sick of living, unwilling to die," and then somehow incorporating another of Edward Hyde's quotes into the 408 cipher as a form of link between the two. However, as Dave Oranchak affirmed "Just because this rare event occurred, doesn’t mean it is anything more than a simple coincidence" - and may just prove the case that we are the "The Most Pattern-Seeking Animal of All".
Here is the text from 'The life of Edward, Earl of Clarendon, lord high chancellor of England,' with the portion of text found in the 408 Cipher having been highlighted below. I am not sure whether the figure 239 was part of the original document, but character 239 in the 408 Cipher is part of this highlighted text and the start of the 15th line (Letter N).
1665 PROJECT ABANDONED 239 "his blessed father and himself as a subject can do from his prince, a nobleman of the best quality, the best allied and the best beloved ; to remove at such a time such a person, and with such circumstances, from his counsels and his trust." The King was not of a mould to resist plain speaking like this, and when not supported by the presence of those who made him their tool and instrument, he seldom managed to make way against the vehemence of Clarendon's rebukes. It could hardly be pleasant for a monarch to be told that what he designs is base ingratitude; that his throne is in danger ; the reputation of his Court in evil savour ; that both require such support as they may be able to get from men of reverence and station, and that he would be mad to alienate any support from such men that may be vouch- safed to him ; yet this was the plain meaning of Clarendon's words. But Charles hesitated to go back, repulsed, to those who had made him their mouthpiece. He remained " rather moved and troubled than convinced." But fortunately Clarendon found an unexpected ally in the Duke of York, who had joined the King and himself at the interview, with the intention, it appears, of supporting the King's purpose. To him Clarendon restated his arguments, and urged him to do the best service to the King his brother " by dis- suading him from a course that would prove so mischievous to him." For this once, the Duke was converted to Clarendon's view, and "prevailed with the King to lay aside the thought of it. "l Once more the Court conspirators 1 Charles not rarely showed a respect for his brother's opinion which was not founded upon any high estimate of his abilities. Clarendon himself remarks this when commenting upon the failure of any attempt to arouse jealousy between the brothers. Charles, he says, " had a just affection for him, and a confidence in him, without thinking better of his natural parts than he thought there was just cause for ; and yet, which made it the more wondered at, he did often depart, in matters of the highest moment, from his own judgment to comply with his brother " (Life, iii. 62).