title: Asciidoc split first table header cell
body: <p>I have following table in asciidoc, for which I want the very first cell to be split diagonally (or by some other means more readable) in the sense that it is clear that the top row is the &quot;to&quot;, the first column is the &quot;from&quot; one:</p>
  <pre><code>[cols=&quot;,&quot;]
  |===
  a|
  To →
  
  From ↓
  
  |Hans
  |Karl
  |Secret gift
  |===
  </code></pre>
  <p>Please note that if I change to <code>[cols=&quot;,&quot;,options=&quot;header&quot;]</code> the spaces of the first cell are removed, making it even harder to understand the table semantics.</p>
  <p>See also <a href="https://stackoverflow.com/questions/45506550/how-can-a-split-diagonally-a-table-header-cell">How can a split diagonally a table header cell?</a> for similar question explaining the requirement in HTML</p>