Poetry in a math text

     In the 1980s, all students at Bloomsburg University were required to take at least one mathematics course and I worked with colleagues to develop a suitable offering -- one that did not require expertise in algebra but which emphasized problem-solving.  Our course became "Mathematical Thinking" -- and I began to develop suitable materials -- eventually writing and publishing Mathematics in Daily Life:  Making Decisions and Solving Problems (McGraw-Hill, 1986).  Each of the twenty-two chapters of this textbook is introduced with a relevant quote.  Chapter 11, "Visualizing the Structure of Information with a Tree Diagram," opens with two lines by one of my favorite poets, Theodore Roethke:

               Once upon a tree              
               I came across a time.

     While preparing this post I searched first my shelves and then online for the Roethke quote -- and, while I found much discussion of its wordplay, I have not found its original publication source.  Moreover, I discovered that  in my text I had misquoted the poet, using "upon" where Roethke had offered "across."  During my search I also found this list of figures of speech with the term hypallage to name the type of word-switching that Roethke has done.  My own preference is, however, to analyze less.  The symmetry of tree and time seems nearly natural. 
     My freshman-level textbook still is available -- for example, at abebooks.com for $1.  You can, however, imagine my disappointment when I read, for one of the available copies, "shows only minor use."

Additional verses scattered throughout the text include:
     the opening lines of Elizabeth Barrett Browning's "How Do I Love Thee?";
     the first stanza of John Godfrey Saxe's "The Blindmen and the Elephant"; 
     the English riddle-rhyme that begins, "As I was going to St. Ives ... ."