LOC's Public Domain Archive
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![[Perspective rule for drawing square structure illustrated with geometrical diagram; figure IV]](https://cache.getarchive.net/Prod/thumb/cdn4/L3Bob3RvLzIwMTkvMDkvMjcvcGVyc3BlY3RpdmUtcnVsZS1mb3ItZHJhd2luZy1zcXVhcmUtc3RydWN0dXJlLWlsbHVzdHJhdGVkLXdpdGgtZ2VvbWV0cmljYWwtOWFkNDU4LTEwMjQuanBn/40/32/webp "[Perspective rule for drawing square structure illustrated with geometrical diagram; figure IV]")