そこはかとなく鏡のような枕ども　【アンケート　夜は何時くらいに寝るのが普通？】

They're vaguely mirror-like pillows.

[Survey: What time do you normally go to bed at night?]
• About 10 p.m.
• About 12 a.m.
• About 2 a.m.
• I don’t sleep
• I sleep during the day