I want to know the answer to the following question:
The Pillow Book was a collection of whose observations of the imperial court?
All the background I'm provided with is that "Murasaki Shikibu's contemporary and rival Sei Shōnagon's revealing observations and musings as an attendant in the Empress' court were recorded collectively as The Pillow Book in the 990s, which revealed the quotidian capital lifestyle.". Is that enough to answer the question?