In the Wikipedia article on hypertext, I was glad to see dictionaries mentioned in the “early precursors to hypertext” section:

Other reference works (for example dictionaries, encyclopedias, etc.) also developed a precursor to hypertext, consisting of setting certain words in small capital letters, indicating that an entry existed for that term within the same reference work. Sometimes the term would be preceded by a pointing hand dingbat, ?like this, or an arrow, ?like this.

What’s interesting to me is that, now that many old dictionaries have been digitized and put online, these pre-hyperlinks have now been converted into actual hyperlinks, fulfilling their original function in a way far more elegant than the original makers of the dictionaries could ever have imagined. Go, the future!