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| | Diptych - Wikipedia, the free encyclopedia |
 | | Holding a diptych so that its gnomon-string is at the correct angle is often finicky, especially near sunrise, sunset and noon, so many later diptychs had magnetic compasses and plumb-bobs to help, but these were luxuries, not necessities. |
 | | Some diptychs also had rough calendars, in the form of pelikinons calibrated to a nodus in the form of a bead or knot on the string. |
 | | Diptychs that combined writing and timekeeping often have a slot on one leaf to hold the gnomon. |
| en.wikipedia.org /wiki/Diptych (814 words) |
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