משנה על ביצה 2:1

One who buries turnips or radishes beneath a vine, if some of their leaves are uncovered, he need not have fear [of having transgressed] kilayim, or the sabbatical year, or tithes and they may also be pulled up on Shabbat. One who plants a [grain of] wheat and [a grain of] barley at one time, behold this is kilayim. Rabbi Judah says: it is not kilayim unless there are two grains of wheat and two grains of barley, or one grain of wheat and two grains of barley, or a grain of wheat, a grain of barley and a grain of spelt.

In three cases Rabban Gamaliel was strict like the words of Beth Shammai.One may not wrap up hot food on a festival for the Sabbath; And one may not join together a lamp on a festival; And one may not bake [on festivals] thick loaves but only wafer-cakes. Rabban Gamaliel said: “In all their days, my father’s house never baked large loaves but only wafer-cakes.” They said to him: “What can we do with regards to your father’s house, for they were strict in respect to themselves but were lenient towards Israel to let them bake both large loaves and even charcoal-roasted loaves.”