Tears of Themis: Artem's Legend of Celestial Romance Invitation
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Artem's paid invitation from Legend of Celestial Romance!
谨以白头之约,书向鸿笺 is pretty much part of a vow spoken when signing a marriage certificate (their equivalent back in those times).
Chinese weddings use red veils instead of white ones, and groom has to be the one to lift it. It's actually usually done with a specific tool, 如意 for the richer families, and 杆秤 for more common ones.