使用CSS在字体大小方面表格单元格高度

I have a table (a calendar, notably). I want to make the calendar not look ugly when nothing is written in for any of the dates, so I want the minimum size of a cell to be equal to four times the font height. (That is, if I have a calendar row with nothing in it, and a calendar row with four lines of text, I want them to be the same size).I have a table (a calendar, notably). I want to