PMFJI, the rectangle/box typically is from a truetype font. When the cmap table does not provide a glyph for a requested codepoint (such as unicode bmp) there is a defined .notdef glyph that is returned.
Looking at my Win7 system, I have coverage for U+262e in Segoe UI Symbol, DejaVu Sans, and Noto Sans Symbols. DejaVu and in particular Noto Sans, being liberally licensed, are becoming de facto standards, at least in cross-platform apps. U+262e, appears to predate the concept of emoji and in these 3 fonts no variation sequences are provided, so the default presentation is probably the best from a compatibility standpoint.