I enjoy exploring the history of the Siddur. Rav Amram and Rav Sa'adia's siddurim are two of the oldest.
One of them, from what I recall has loads of "instructions" some of which explain halachot and occasionally explanations into the phrasing, many of which is no longer used, today. My Hebrew is quite good, but, if there are any English translations for any of these, that would make things a bit easier, esp. if I'm conducting classes with others. Is anyone aware of any English translations?