Example of a semi-orthogonal matrix with a condition on the norm of its rows

Question

Let $m>n$. I would like to find an example of a matrix $M \in \mathbb{R}^{m \times n}$ such that the columns of $M$ are orthonormal vectors (for the euclidean norm), and such that the maximal euclidean norm of the row vectors of $M$ are of order $\sqrt{n/m}$. Is there a simple way to do this ?