What was the crysistor?
I suspect it might have been the conflation of cryosistor (a completely different germanium cryogenic unijunction-like device that worked on the principle of impact ionization) and crytron (not to be confused with the krytron which is used to make loud noises). 



I think he was referring specifically to the crytron and got the name mixed up a bit in his memory. 



The chapter is not error-free (for example, it refers to "new low-temperature superconductors" which would not be an advantage, especially compared to liquid helium).

Here is the actual quote, courtesy of Google books: 



The IBM paper describing the crytron which I linked above was published in October of 1957, so it would have been fresh news in 1959 when Mr. Wilensky graduated.