(See post I.) Perhaps the content of the post is given away by its title.
Be that as it may, have a look at at this excerpt from the פיטום הקטורת service on page 31:
The text says that Cyprus wine was used to steep the incense mixture in the Temple, to make it more pungent. However, מי רגלים mei raglayim would have been an even better mixing agent, but it wasn't decent for use in the Temple. Why not?
Because it is urine. I'm sure most of us know that our relationship to human and animal waste today tends to be very different from what it was in the past. We may know of manure, but most of us don't get that close to it. And certainly we don't think of urine as a cleaning agent, but it is an excellent source of ammonia, and it was used to clean clothes and prepare dyes, among other things. Our waste disappears quickly, and its scent with it.
However, urine is still urine. So even though it would have been even better than Cyprus wine, it wasn't used in the incense.
As you can see, the Birnbaum siddur delicately declines to translate mei reglayim. I really would like to compare it with other English siddurim of the period, but I cannot at the moment.
However, I can compare it with a British mahzor from 17961:
It is interesting that it too simply has mea raglayem, but a footnote says urine. If I had to guess, I'd say that in late 18th century England some people prayed in English, and David Levi, the translator, preferred to have people read mea raglayem when they prayed, but felt fine letting these people know what it meant. Obviously the sensibilities of some people in another land 150 years later are not to be found in or understood through this example.
Also, here is the acknowledgments from the original 1949 editions, removed in subsequent editions:
(Yes, that's Noam Chomsky's father--for the two readers that didn't know.)
Inside the introduction (later removed) is a list of scholars which influenced him: Israel Abrahams, Seligmann Baer, Abraham Berliner, Ismar Elbogen, Louis Finkelstein, Michael Friedlander, Louis Ginzberg, Wolf Heidenheim, Abraham Idelsohn, Pool and Yaavets (at first I though this was R. Ya'akov Emden, who he quotes in the siddur, but I believe it refers to another scholar of the liturgy).
1 מחזור לשבועות כמנהג פולין The form of prayers, for the Feast of Pentecost. According to the custom of the German and Polish Jews, carefully translated from the original Hebrew. By David Levi. London 1796.